Reiss notes that in Connecticut, for example, the rate of religious opt-outs from school vaccine requirements grew from 1.7 to 2.7 percent between 2012 and 2019, even though there was no corresponding change in the state’s religious composition. In California, the rate nearly quadrupled between 1994 and 2009. Rising opt-out rates have correlated, as you’d expect, with rising infections. In 2019, two decades after measles was declared “eliminated,” the CDC reported 22 outbreaks and 1,249 cases—the highest number since 1992.

Reiss laid out the problem bluntly in a 2014 article : “First, people lie to get a religious exemption. Second, U.S. jurisprudence makes preventing such abuse very hard.”

State legislature may have had Christian Scientists in mind when they wrote exemptions into law. The trouble is that carveouts can’t legally be limited to any particular denomination, or even to members of organized religion. In 2001, for example, a federal judge ruled that Arkansas’ vaccine exemption violated the Constitution because it only applied to members of a “recognized church or religious denomination.” Arkansas responded by changing the law to allow parents to claim a “personal belief” exemption, a path that 14 other states currently follow. Research has found that these states grant more non-medical exemptions than states that limit them to religious claims.

While the language of religious objections typically refers to someone’s “sincerely held belief,” judges are understandably wary of trying to read someone’s heart and mind. That creates room for mischief when it interacts with a cultural shift that constitutional law scholar Robert Post calls the “protestantization of religion”—the growing feeling that religious doctrine is not handed down by hierarchical organizations, or even governed by internal consistency, but is a question of individual private belief. Everyone is potentially a religion of one, an echo of the Supreme Court’s 1879 warning about permitting “every citizen to become a law unto himself.”

If America’s religious objectors aren’t taking their cues from official teachings, where are they getting them? To some degree, the answer seems to be Donald Trump, the Republican Party, and right-wing media. The result is a “religious” opposition to vaccine mandates that is at times indistinguishable from a political stance.

A recent Washington Post article captures the phenomenon in detail. A pastor in Tennessee urges his audience of “patriots” to run for office to fight Covid restrictions. Protestors at a Florida school board meeting wear shirts that read “Jesus is my savior, Trump is my president” and accuse board members of being “demonic entities.” A nurse leading a protest against vaccine mandates for medical workers in Pennsylvania asks the crowd “to cheer if they loved America, freedom, ‘God-given rights,’ and Jesus.”

These are extreme cases. But they illustrate the volatility of religious exemptions at a time when opposition to public health measures is itself beginning to resemble an article of faith. In those conditions, the problem is not just that people will say their objections are religious when in fact they aren’t. It’s that they’ll say their objections are religious and mean it.

When it comes to employer-imposed mandates, the 1964 Civil Rights Act requires companies to offer “reasonable accommodations” based on employees’ religious beliefs, as long as they aren’t a burden on the business. As for the government, despite the federal and state religious freedom laws, there’s a fair bit of case law suggesting that religious exemptions aren’t required. Following measles outbreaks, the legislatures of California, New York, and Maine all recently eliminated religious exemptions from school vaccine mandates, and those repeals have held up in court.

But that doesn’t mean the current Supreme Court majority will be OK with Covid vaccine mandates that don’t include a religious opt-out. The pendulum of religious liberty law can swing dramatically. The 1990 Scalia decision was so unpopular that a near-unanimous Congress quickly passed the Religious Freedom Restoration Act, which reinstated the “strict scrutiny” standard for federal laws. Twenty-one states have their own version of the statute. Several of the Court’s conservative justices have argued for overturning the 1990 ruling entirely.

So far, cases challenging mandates around the country are coming out in different ways. A federal judge in Louisiana ruled that a private university that uses public facilities can’t require vaccinations. In New York, a federal judge has temporarily blocked the state from enforcing its mandate against health care employees who raise a religious objection. Other challenges have failed: Most notably, a group of students sued Indiana University over its mandate, but Justice Amy Coney Barrett, a conservative Catholic appointed by Donald Trump, rejected their appeal. In that case, the university offered a generous accommodation, allowing students to be tested regularly. We still don’t know what would have happened if the school had instead told unvaccinated students they weren’t welcome on campus.

Two dynamics help explain why these cases are playing out so chaotically. First, most of the case law on vaccine requirements deals with schoolchildren, where mandates are especially easy to defend. An adult who opts out of vaccines for their child is risking the health of someone too young to make their own decisions. Not so for mandates that apply to grownups.