A Green Lantern is supposed to uphold certain principles of his/her/its duty. These principles include:
- The protection of life and liberty within the assigned sector.
- Following the orders of the Guardians without question.
- Noninterference with a planet's culture, political structure, or its population's collective will.
- Acting within local laws and obeying the local authority within reason. (Presumably, The Guardians' orders can overrule this when necessary).
- Taking no action against anyone or anything until they are proven to be a threat against life and liberty.
- Avoiding the use of equipment, resources or authority of The Corps for personal gain.
- Showing respect for and cooperating with other members of the Corps and the Guardians.
- Showing respect for life which includes restraint of force unless there is no reasonable alternative.
- Giving top priority to the greatest danger in the assigned sector.
- Upholding the honor of the Corps.
Ten new Laws have been added to The Book of Oa, but so far only the first four have been revealed.
- Lethal Force is authorized to be used against the Sinestro Corps.
- Lethal Force is authorized against all enemies of the Green Lantern Corps.
- Physical relationships and love between Green Lanterns is forbidden within the Corps. (ABOLISHED)
- The Vega System is no longer outside of Green Lantern Corps' Jurisdiction.
When new laws are written, the book's language is revealed as Interlac, the universal language of the 30th and 31st Century United Planets and the Legion of Super-Heroes. The third law was abolished due to Kyle Rayner explaining the need for it to be done away with and Salaak's continued disgust with the Guardians.
Is the Forbidden Chapter of the Book which tells the prophecy of the Blackest Night, the prophecy states:
A face of metal and flesh shall speak of the secrets of the 52.
Fear will rise. Willpower will gather. And a wave of light will unleash the truth behind the power of the ring. This prophecy was uncovered long ago by Abin Sur on the planet Ysmault, but he was forbidden to speak of it.
Green Lanterns are closely monitored by the Guardians. If any Lantern violates a mandate he will be held on trial and if the Guardians consider it necessary a punishment will be dealt. These are some of the known options.
- Personal supervision by the Guardians on Oa.
- Temporary exile from the Lantern's homeworld.
- Ritual Trial of Endurance - a Lantern must attempt a dangerous passage through the Anti-Matter Universe.
- Reassignment to another sector or Corps position.
- Expulsion from the Corps.
- Prime Duty - When Superboy-Prime was an Oan prisoner, guard duty was used for punishment.