There are many species in Star Wars, both sentient and non-sentient, that are in some fashion resistant to influence or detection through the Force. However, most people seem unaware how this insubordination to Force suggestion transpires, and others even translate this immunity to others by holding Force-resistant species as a standard, saying that if a Jedi can’t affect a certain species with the Force, then that attests to a limitation in their Force power. Both of these issues will be addressed here. Before continuing, I will not be covering every species with some resistance to the Force. The Yuuzhan Vong notably will not be dealt with here; the Vong race will receive its own “Force Misconceptions” blog at some point in the future, because there are countless misunderstandings about them.

To begin, let’s address species that displayed shielding to Force abilities in the movies: Hutts and Toydarians. We all should be familiar with these two; both resisted Mind Tricks in the movies, Jabba the Hutt from Luke Skywalker and Watto from Qui-Gon Jinn. But how did Jabba and Watto resist the Jedi’s Force suggestion? First, in the novelization of Return of the Jedi, Jabba noted that his brain patterns are very distinct from those of humans, which would inhibit Luke’s ability to arrest Jabba’s thoughts and subject them to his own influence.

Bib stood proudly before Jabba. “Master, I present Luke Skywalker, Jedi Knight.”

“I told you not to admit him,” the gangster-slug growled in Huttese.

“I must be allowed to speak.” Luke spoke quietly, though his words were heard throughout the hall.

“He must be allowed to speak,” Bib concurred thoughtfully.

Jabba, furious, bashed Bib across the face and sent him reeling to the floor. “You weak-minded fool! He’s using an old Jedi mind trick!”

Luke let all the rest of the motley horde that surrounded him melt into the recesses of his consciousness, to let Jabba fill his mind totally. “You will bring Captain Solo and the Wookiee to me.”

Jabba smiled grimly. “Your mind powers will not work on me, boy. I am not affected by your human thought pattern.”

--Taken from Return of the Jedi

What about Toydarians? Sources have told us that Toydarians’ bodily structure also contributes dissimilar mental facilities and that Hutts and Toydarians both possess adamant wills that are difficult to subjugate through Force suggestion.

Another unique trait of this species is its brain structure. While this is seemingly no more complex than that of an average human or other sentient species, Toydarians are able to resist attempts at mind control and Force domination.

--Taken from The New Essential Guide to Alien Species

Both Hutts and Toydarians possess varying degrees of mental strength that can make them immune to Jedi mind tricks. In an event from the year 4 A.B.Y. that has since become the stuff of legend, Luke Skywalker found himself unable to mentally persuade Jabba the Hutt to release Rebel prisoners, and had to resort to a backup plan.

A personal log of Darth Vader, recovered from his fortress on Vjun, revealed Vader’s disturbing perspective regarding Toydarians. It should be noted that Vader’s disposition may have been influenced by Anakin Skywalker’s relationship to Watto, the Toydarian junk dealer and slaver who was young Anakin’s “master” on Tatooine. Although Shmi Skywalker’s recovered journal suggests that Watto was a relatively benevolent master, it is conceivable that Vader’s memories of Watto were unfavorable. Furthermore, the identity of the “Toydarian subject” mentioned in Vader’s recordings remain unknown, but records from Tatooine preclude the possibility that it was Watto.

These creatures have become such an irritation that every time I see one I want to strike it down with my lightsaber. Be that as it may, I interviewed a Toydarian subject who showed a great amount of resistance to Force suggestion, up to the point that I created physical discomfort. I found that they can be easily intimidated by a demonstration of strength. And it proved relatively simple to cause it to expire, merely by making its existence extremely painful. Ultimately, though it showed a great degree of willpower, it was no match for the power of the Force.

--Taken from Jedi vs Sith: The Essential Guide to the Force

So the issue is the wavelength of the species’ thoughts and willpower. That partially answers the question, but is there anything else? Does this inability to Mind Trick Hutts or Toydarians speak of inherent weakness on the parts of Luke and Qui-Gon as telepaths, or is there something more complex at work? Recent stories have informed us there is. Bowspritz, a Jedi biologist, elucidated in The Jedi Path that Hutts and Toydarians innately repel suggestion through the Force as a result of biological adaptions.

My specialty is alien biology, and as a Jedi I recognize that the fundamental unifier of all life is the Force. It is fascinating how the Force inspires such a variety of change and adaption, even allowing species to develop barriers that redirect the Force’s natural flow. Because such evolution can be found among recognized sentient beings, you should be able to identify these species on sight if you wish to use your Jedi abilities to their fullest.

Hutts You and your Master will probably run across a Hutt’s thugs long before you meet an actual Hutt, but don’t use mind tricks if you’re brought before their boss! Hutts are notoriously difficult to influence or read through the Force. Their elusiveness has been a struggle for the Jedi since our forebears left Tython.

Toydarians These fascinating beings have lighter-than-air gases in their bellies that enable flight in standard or less-than-standard gravities. But remember that Toydarians are resistant to mind tricks, illusions, and telepathic suggestions. They are well aware of this fact and boast that they can easily outsmart a Jedi. Do not haggle with a Toydarian vendor!

--Taken from The Jedi Path: A Manual for Students of the Force

Now, how can biological evolution impact a species’ connection to the Force? The answer lies in Bowspritz’s remark that the Force itself can inspire evolutionary adaptation, which can alter a species’ place in the Force. This makes sense, as the Force pervades all forms of life and is the collective consciousness of life; in fact, it generated life from itself and instigated life’s natural growth. Though the Force is not deterministic (unless a being willingly surrenders to the Force’s directive), the Force can motivate mindsets and emotions, which a decision-making being can accept or deny. And if the Force can galvanize a sentient being to action or provide the capacity for choice, it can certainly alter biological compositions.

After all, the Force does pronounce life in the form of biological makeup. The Force might be present in everything, whether organic or inorganic, but the Force manifests itself in living beings most as opposed to inorganic matter. Droids, for instance, cannot be Force sensitive despite them existing in the Force, while virtually any sentient life can be Force sensitive (even sentient crystals). While there is validity in Yoda’s statement that the “crude matter” of living beings don't advertise the truth of their person and in Luke’s statement that living entities really are “beings of light,” the Force is most potent in organic life and has a profound influence on it. Even since the OT, this was displayed in a minor way when it was established that Force sensitivity can be inherited from a being’s lineage; Luke and Leia acquired their Force sensitivity from Anakin, as the example given in the films. In the EU, Force sensitivity passed along the Halcyon lineage lacks skill in Telekinesis but has an aptitude for Illusions and Absorption. As well, one of the primary applications of Sith alchemy is the administration of physical enhancements in creatures, which often ingrains in them a stronger connection to the dark side. Naturally then, it follows that the Force could also affect life’s evolution.

To illustrate this point in the most detail, let’s look at two other cases of Force-resistant species, the Yinchorri and the ysalamiri. The Yinchorri, like Hutts and Toydarians, are resistant to mental manipulation, and ysalamiri are notorious for their Force-neutralizing fields. It is commonly misunderstood that ysalamiri are simply absent in the Force and can just sever others in the Force who are near them, but this is not entirely accurate. In their accounts on them, Tionne Solusar and Bowspritz explain that ysalamiri actually use the Force in order to negate it within a restricted range.

Yinchorri These reptilians are immune to mental manipulation and cannot have their internal balance disrupted by advanced Force techniques. Their warriors also wear cortosis armor, so don’t pick a fight.

--Taken from The Jedi Path: A Manual for Students of the Force

Ysalamiri are salamander-like, nonsentient creatures native to the planet Myrkr. Sessile, arboreal, and equipped with strong claws that draw nutrients from Myrkr’s mineral-rich trees, they cling to their branches with such tenacity that special knowledge is required to remove them without killing them. The ysalamiri’s most remarkable characteristic is its ability to create a “bubble” in which the Force cannot exist. More specifically, the Force cannot be manipulated within such a bubble, which can extend up to ten meters in radius from a single ysalamiri. In groups of ysalamiri, such bubbles can extend and overlap, resulting in vast areas in which the Force cannot be used on Myrkr.

Talon Karrde, the founder of the Smugglers’ Alliance, was based on Myrkr when Grand Admiral Thrawn cam to acquire ysalamiri, which Thrawn then used to protect himself from Force-users. To prevent the ysalamiri from dying after they were removed from the trees and to allow for their use as a mobile means of defense against Force-users, Imperial engineers fashioned special nutrient-infused pipe frames that could be worn on the backs of individuals.

The ysalamiri’s incredible ability to disable or “push back” the Force is part of a natural defensive mechanism that protects them from another indigenous species on Myrkr, the Force-sensitive pack animals called vornskrs. Cunning predators, vornskrs are fur-covered canine animals with sharp teeth and poison-coated, whip-like tails. Their attunement to the Force seems to be tied directly to their hunting instincts, as they are naturally able to detect Force-users, and also use this ability to hunt ysalamiri. They regard any Force-user as prey, and will not hesitate to attack Jedi.

--Taken from Jedi vs Sith: The Essential Guide to the Force

Why shouldn’t animals use the Force? That was my thought when I first heard of the phenomenon as an Initiate, before I started down the path that ultimately gave me the honorific of beastmaster. Since that time I’ve seen plenty of evidence that the Force can be an evolutionary advantage, just like spines or antlers.

Central to any such discussions are the vornskrs and ysalamiri of a classified world. Their abilities caused the Council to quarantine the entire system. Vornskrs are quadrupedal predators that can sense the Force and can use that sense to home in on their prey. So because Jedi are strong in the Force, they appear the biggest and tastiest meal a vornskr has ever encountered. Beware the enemy that utilizes this ability to hunt Jedi.

Though vornskrs are organic “Jedi detectors,” their Force abilities are negligible compared to those of the ysalamiri—arboreal lizards that create bubbles or voids in the Force that hide their energy from predators like vornskrs. Enough ysalamiri clusted together can generate a void large enough to disable an army of Jedi from using the Force.

--Taken from The Jedi Path: A Manual for Students of the Force

This changes the matter considerably. If ysalamiri were somehow just removed from the Force and could assert that status onto others around them, that would be evident in how Force sensitive’s respond to it, as there would be little solution to a situation like that, but if a character could circumvent the effects of ysalamiri’s Force bubbles, then that further affirms the idea that ysalamiri use the Force to void the Force, because Force-derived skills can be counteracted. And there is an instance of that; Luke once briefly noted during the Vong War that he had practiced preventing himself from being cut off from the Force by ysalamiri.

"Would she? Obi-Wan and Yoda never talked about what the distant future held for me. Maybe if I hadn't spent the past few years trying to learn how to overcome ysalamiri and tune my lightsaber to cleave cortosis ore, I'd know what course the Jedi should take now. It's the dark side that calls constantly for aggression and revenge—even against the Yuuzhan Vong. The stronger you become, the more you're tempted." Luke gazed at his wife. "Maybe Jacen's right about there being alternatives to fighting."

--Taken from Agent of Chaos I: Hero’s Trial

This also means that if the Force itself is what enforces an ysalamiri’s Force-retardant bubble and fomented Hutt, Toydarian, and Yinchorri Force-resistances, among others, that there might be a way to overcome the latter three species’ Force-resistances as well. But to bypass a Force-resistance, you need to isolate the root of that resistance. We know that the Force engineered a natural environmental adaption in species like Toydarians or Yinchorri, but that clarification is still too simplistic. Through what means did the Force accomplish this? How exactly is the Force linked to biological functions? What caused it to modify a species’ reaction to it? Darth Plagueis answers this.

During his experiments on midi-chlorians, Plagueis finds that midi-chlorians can adjust a species’ connection to the Force. Midi-chlorians are the intermediaries between the Force and organic life that interpret the Force’s will to living beings, and because midi-chlorians are biological and serve the Force, they can protect a species from environmental or predatory dangers through the evolutionary process as the Force directs them to. Plagueis uncovered this relationship between adaptions and midi-chlorians while operating on a Yinchorri subject and attributed the Force-resistance that midi-chlorians cultivated in Yinchorri to other species with natural Force adaptions as well. He found that by his manipulation of midi-chlorians, he could force the midi-chlorians to drop the defenses that shield a Yinchorri’s mind and subsequently Mind Trick the Yinchorri successfully.

Holding Qayhuk’s baleful gaze and motioning with his hand, Damask said, “You have no interest in seeing Yinchorr seated in the Senate.”

Qayhuk took umbrage. “Why else would we have journeyed all this way?”

“You have no interest in seeing Yinchorr seated in the Senate,” Plagueis repeated.

Qayhuk glanced at his green-skinned brethren, then looked at Hill. “Is Magister Damask deaf or in ill health?”

Hill turned to Damask in concern but said nothing.

Damask concealed his astonishment. As rumored, the Yinchorri were apparently resistant to Force suggestion! But how was it possible that midi-chlorians in a being of relatively low intelligence could erect an impenetrable wall against the influence of a Sith? Was this some sort of survival mechanism—the midi-chlorians’ way of protecting the consciousness of their vessels by refusing to be manipulated? He would need to possess one of these beings to learn the secret.

A gift to Damask from the Council of Elders on the occasion of Yinchorr’s seating in the Senate, the towering reptilian condemned murderer shuffled to the center of the energy field that defined his cage on Aborah and, with confusion contorting the features of his beaked face, prostrated himself on the permacrete floor and mumbled in Basic: “I’m honored to be here and to perform whatever tasks you require of me.”

Standing at the field’s shimmering perimeter, 11-4D pivoted his head toward Plagueis. “Congratulations, Magister. At last he responds to your suggestion. You have undermined his resolve.”

That resolve, Plagueis had learned after more than two years of experimentation on the Yinchorri, was in fact a kind of Force bubble fashioned by the turtle-like alien’s limited number of unusually willful midi-chlorians. This suggested that the Yinchorri was actually strong in the Force, despite his pitifully low count. The discovery had come as a breakthrough, and Plagueis was still grappling with the implications.

The Force bubble itself was similar to those generated by creatures that drew on the Force to avoid predation by natural enemies. The relationship between the arboreal ysalamir and its adversary, the vornskr, provided a curious example, in that the latter was attracted to the former by the very mechanism the ysalamir employed as a defense. Where an extremely low midi-chlorian count might have bolstered the odds of survival, nature had instead made the ysalimir species strong in the Force. So strong, in fact, that several of the creatures acting in concert could create a Force bubble encompassing kilometers rather than meters. In a sense, the Jedi Order had done the same on a galactic scale, Plagueis believed, by bathing the galaxy in the energy of the light side of the Force; or more accurately by fashioning a Force bubble that had prevented infiltration by the dark side, until Tenebrous’s Master had succeeded in bursting the bubble, or at least shrinking it. How the Order’s actions could be thought of as balancing the Force had baffled generations of Sith, who harbored no delusions regarding the Force’s ability to self-regulate.

The Yinchorri former convict wasn’t the only new addition to Plagueis’s island facility. In the eleven years that had elapsed since the capture of Venamis and the recruitment of Sidious, Plagueis had collected more than a dozen beings of diverse species and had been subjecting them to a wide range of experiments involving volition, telepathy, healing, regeneration, and life extension, with some promising results. As for the Bith would-be Sith Lord, he was alive and well, though kept comatose more often than not, and always under the watchful photoreceptors of 11-4D or a host of custodial droids.

Plagueis hadn’t lost interest in Venamis by any means, but the Yinchorri’s immunity to Force suggestion—an immunity the species shared with Hutts, Toydarians, and others—had provided him with a new line of investigation. Unlike ysalamiri, which created a Force bubble in the presence of danger, the Yinchorri were in a perpetual state of involuntary immunity to Force suggestion. The fact that immunity was in a sense hardwired into them meant that the ability was an adaptation, prompted by a past threat to the survival of the species. To Plagueis, it meant that the Yinchorri’s midi-chlorians had evolved to provide protection to a species that was naturally strong in the Force. If that were indeed the case, then the Yinchorri were living proof that the Sith of the Bane line had been on the right path from the very start.

In the same way that the pre-Bane Sith had been responsible for their own extinction, the great dark side Lords of the past had doomed themselves to the nether realm through their attempts to conquer death by feeding off the energies of others, rather than by tapping the deepest strata of the Force and learning to speak the language of the midi-chlorians. Plagueis was finally learning to do that, and was just beginning to learn how to persuade, prompt, cajole, and coax them into action. Already he could command them to promote healing, and now he had been successful in enticing them to lower their defenses. If he could compel a murderous Yinchorri to become peaceful, could he—with a mere suggestion—accomplish the opposite by turning a peaceful being into a murderer? Would he one day be able to influence the leaders of worlds and systems to act according to his designs, however iniquitous? Would he one day conquer not only death but life, as well, by manipulating midi-chlorians to produce Forceful beings, even in the absence of fertilization, as Darth Tenebrous might have attempted to do with gene-splicing techniques and computers?

Perhaps.

But not until the singular flame of the light side was extinguished from the galaxy. Not until the Jedi Order was stamped out.

--Taken from Darth Plagueis

This puts everything into perspective. The Force itself originated the adaptions in species such as Yinchorri, Hutts, Toydarians, ysalamiri, and several others with resistances to Force powers and did so through the activity of midi-chlorians present in these species as an evolutionary growth to protect that species. That elaborates on how any species could universally and involuntarily repulse the influence of the Force, because it would be near to impossible to do that without the Force’s consent. It also clarifies that there is no defect in the power of Jedi or Sith for failing to appropriate their powers against these species, because the midi-chlorians, actuators of the Force’s will that they are, implanted these adaptions with the Force itself, and even then, there are some like Luke and Plagueis who have exercised methods of overturning these resistances.