(For an introduction to this series of posts, see here.)
The RFRA religious exemption regime may seem less exemption-friendly than the Sherbert/Yoder-era constitutional exemption regime, precisely because it is only statutory. If Congress (or, for a state RFRA, a state legislature) dislikes an exemption that courts have recognized, it can pass a new statute rejecting that exemption. Congress can even block such exemptions proactively, for instance by saying up front that some statutes won’t be subject to religious exemptions. (Some state legislatures have indeed done that.)
The 1993 Congress could not bind future Congresses — only a constitutional amendment can do that — and it didn’t purport to try. RFRA makes clear that future statutes could be excluded from RFRA’s scope if “such law explicitly excludes such application by reference to [RFRA].” It also seems likely that they would also be excluded if “the plain import of a later statute directly conflicts with an earlier statute” (though courts are reluctant to find such direct conflicts because of the “powerful presumption against implied repeals”). As a result, exemptions recognized under RFRA, unlike exemptions recognized under the Free Exercise Clause in the Sherbert/Yoder era, are at the mercy of the legislature.
It’s possible, though, that the RFRA regime may sometimes prove to be more religious-exemption-friendly than the old constitutional exemption regime, precisely because it is statutory. A court may be reluctant to accept a close constitutional claim precisely because accepting it would permanently bind the legislature. Even a judge who thinks that granting a religious exemption from (say) a peyote ban might not cause that much harm, and who thinks the legislature might not have considered this particular question when it banned peyote, may be hesitant to tie the legislators’ hands by declaring that [...]