Defining religion

Professor Friedman reports on an interesting case out of California: 

[A] California federal court held that even though the belief is sincerely held, veganism is not a "religion" for purposes of the First Amendment or RLUIPA. The issue arose in the context of a prisoner's request for a vegan diet. The court held: "Plaintiff's veganism ... does not address 'fundamental and ultimate questions;' it has no formal and external signs. Plaintiff does not allege the existence of any larger body of adherents to which he belongs. Instead, he describes his veganism as a 'right and appropriate way to live.' .... [Therefore] Plaintiff's dietary regimen is a purely secular lifestyle choice, not protected by the Free Exercise Clause."

What do we think of this definition of "religion"?