relevant to some posts I'll be putting up about tomorrow's Gonzales v. O Centra Vegetal Supreme Court argument:
Say that you feel a religious obligation to use a prohibited drug — hoasca (the drug at issue in O Centro), peyote, marijuana, or LSD. Or say that you’re a landlord who feels a religious obligation not to rent to unmarried couples (or same-sex couples), even though state law bars marital status discrimination or sexual orientation discrimination in housing. Or say that you feel a religious obligation to help someone commit suicide, in violation of state law — or a religious obligation not to testify against your parent, your child, or a coreligionist, even when you have a legal duty to do so. Should you be entitled to an exemption from the generally applicable law, because of your religious beliefs? Or should the government be free to apply the law to you just as it does to others?
Until 1963 (more or less), the rule was what I call the statutory exemption model -- religious objectors got exemptions if and only if the statute provided for one (as, for instance, draft law historically had). Then in Sherbert v. Verner (1963), the Supreme Court adopted the constitutional exemption model, under which sincere religious objectors had a presumptive constitutional right to an exemption.
Of course, a constitutional exemption model can never simply say "religious objectors get an exemption"; a wide range of generally applicable laws -- murder law, theft law, rape law, and so on -- must be applicable even to religious objectors. Even as to more controversial cases, such as bans on race discrimination in education, or generally applicable tax laws, the Court found (even under Sherbert) that religious objectors' claims must yield. To distinguish cases where religious objectors win from those in which they lose, the Sherbert-era Court used what it called "strict scrutiny" -- religious objectors must prevail unless applying the law to them is the least restrictive means of serving a compelling government interest. But while the "strict scrutiny" test in race and free speech cases was generally seen as "strict in theory, fatal in fact" (Gerry Gunther's phrase), almost always invalidating the government law, in religious freedom cases it was "strict in theory, feeble in fact" (Sager & Eisgruber's phrase); the government usually won, and religious objectors won only rarely.
Then in 1990, the Court changed course: In Employment Division v. Smith (1990), a 5-Justice majority returned to the statutory exemption regime, and rejected the constitutional exemption regime. So long as a law doesn't discriminate against religious objectors, but generally applies to people regardless of their religiosity, it's constitutionally valid. If religious objectors want an exemption, they need to go to the legislature. (This is an oversimplification, but let's go with it for now.)
Then in 1993, Congress enacted the Religious Freedom Restoration Act, which gave religious objectors a statutory presumptive entitlement to exemption from generally applicable laws (subject to strict scrutiny). In City of Boerne v. Flores (1997), the Supreme Court held that RFRA exceeded federal power when applied to state laws, but didn't touch it as to federal law. Since 1997 (and in some measure before), quite a few states enacted similar state-level RFRAs as to state law. Therefore, the rule now is that the federal RFRA applies to federal statutes, and state RFRAs to state statutes in those states that have such state RFRAs. Religious objectors in those jurisdictions may demand exemptions from generally applicable laws, which the government must grant unless it can show that applying the laws is the least restrictive means of serving a compelling government interest.