Seems like Zen Buddhist lineage isn't enough to convince prisons.
I know many believe "Well prisoners can't pick and choose, they had their choice!" - but that would exclude people being held in detention before conviction - and morally dubious crimes or false convictions / detentions.
(Bolding my own) I know it's an older article, but points to some nice cases involving plant-based-diet and prison.THE HUMBOLDT COUNTY JAIL MUST HONOR PETITIONER'S REQUEST FOR A RELIGIOUS DIET BASED ON HER SINCERELY HELD RELIGIOUS BELIEF
Therefore, the Humboldt County jail should have to prove that an inmate's veganism is not a sincerely-held religious belief or permit an inmate access to the internet or a religious library to substantiate the claim.
Under well-settled law that the Humboldt County jail is oblivious to, it is unconstitutional for jail functionaries to determine whether a vegan/vegetarian diet is required or preferred by the majority of pagans or Jews or Buddhists or, such Christian sects as the Seventh-day Adventists (see LaFevers v. Saffle, 936 F.2d 1117 (10th Cir. 1991) or Rastafarians (see Oluwa v. Gomez, 133 F.3d 1237, 1239 (9th Cir. 1998) (summary judgment for petitioner is reversed and case remanded to permit prison officials a chance to challenge Oluwa's claim of belonging to the Rastafarian religion and the vegan diet required by that religion) or Hindus or Sikhs or Zen Buddhists (Spies v. Voinovich, 173 F.3d 398 (6th Cir. 1999) (court ignores the above supreme court authority and rules that because the inmate stupidly conceded that a vegan diet was not required by his Zen Buddhist faith, that it was sufficient that the prison provided him a vegetarian diet); but see id. at 407-411, Justice Moore's dissenting opinion, chastising the majority for ignoring the above authority that it is irrelevant whether all the sects of a particular religion requires a particular diet). The sole issue is whether petitioner's belief in a particular diet is a sincerely held religious belief, no matter how unorthodox or fringe. The evidence is undisputed that petitioner's belief is sincere and religious-based, as petitioner's declaration and other evidence proves. The Jail May Not Starve Petitioner While It Tries To Make Her Somehow Prove Her Religious Belief; The Jail Should Provide The Religious Diet Until It Proves The Belief In A Certain Diet Is Insincere Or Not Based On A Religious Belief