Illustration by Tom Bachtell

One of the surprises of President Obama’s second term has been the prominence of a question that seemed peripheral to his first: the meaning of religious freedom. For years, opponents of the Affordable Care Act framed their objections in terms of economic freedom, but now some of the most noticeable challenges are coming from Christian groups who oppose the law’s contraception-coverage requirement. In January, the Supreme Court extended a temporary injunction for the Little Sisters of the Poor, a Catholic order that objects to having to file a form to obtain a religious exemption from the requirement. (When an organization files, the government effectively subsidizes its insurance provider, so that the employees’ contraception is still covered.) The Supreme Court will soon hand down a decision in the case of Hobby Lobby, the craft-store chain that strives to operate “in a manner consistent with Biblical principles.” One of those principles, in Hobby Lobby’s view, forbids it to pay for those contraceptives which it considers tantamount to abortion. If the Court rules in the store’s favor, the decision would be a small setback for the A.C.A. But it would be a big advance for the religious-freedom movement, which wants courts to recognize that for-profit corporations can be believers, too.

The argument over same-sex marriage is likewise shifting. Last year, when Charles J. Cooper appeared before the Court to defend California’s ban on same-sex marriage, his argument was scrupulously secular. Cooper told the Justices that California had good reason to treat heterosexual relationships differently, because California cares about children, and because “the natural procreative capacity of opposite-sex couples continues to pose vitally important benefits and risks to society.” He didn’t persuade the majority, and perhaps he didn’t persuade himself: a new book, “Forcing the Spring,” by Jo Becker, reports that Cooper’s position on gay marriage continues to “evolve,” just as Obama’s once did. (Cooper’s stepdaughter has become engaged to a woman.) Many opponents have evolved, too. They have decided that if same-sex marriage can’t be stopped in the name of “society” it can be resisted in the name of religious freedom.

The heroes of this movement are people like Jack Phillips, a baker from Colorado, and Elaine Huguenin, a photographer from New Mexico—Christians who refused to supply their services to same-sex weddings and were sued for discrimination. In response to these cases, a number of Republican-controlled state legislatures introduced “religious freedom” laws. Governor Jan Brewer vetoed Arizona’s bill after leading politicians, including John McCain, objected and business leaders warned of ill effects, including the possible loss of next year’s Super Bowl. Measures in Kansas and Idaho failed, too. But last month, in Mississippi, Governor Phil Bryant signed a bill decreeing that “state action shall not substantially burden a person’s right to the exercise of religion” without “compelling justification.” Supporters cited the example of a church whose relocation had been blocked by a local zoning ordinance. Opponents asserted that the law would harm the state’s gay population: GLAAD called it a “thinly masked attempt to discriminate against L.G.B.T. people under the guise of ‘religious freedom.’ ”

The First Amendment—which holds that “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof”—was worded so as not to circumscribe the religious arrangements in place in some states. (In Massachusetts, taxes subsidized “Protestant teachers” until 1833.) Over time, though, and in light of the Fourteenth Amendment’s guarantees of “equal protection of the laws,” the courts have broadened its meaning. They have regularly been petitioned, often successfully, by believers seeking exemption on religious grounds from military service, educational requirements, or taxes. Then, in 1990, the Supreme Court issued an unexpectedly broad ruling against members of the Native American Church who had been denied unemployment benefits after the drug-rehabilitation center where they worked fired them for ingesting peyote, which their church considers a sacrament. Writing for the majority, Justice Antonin Scalia said that a ruling for the plaintiffs “would open the prospect of constitutionally required religious exemptions from civic obligations of almost every conceivable kind.” Legislators from both parties, spurred on by an unusual coalition of religious leaders and civil libertarians, responded by drafting the Religious Freedom Restoration Act, which President Clinton signed into law, in 1993. The law provides that “government shall not substantially burden a person’s exercise of religion.” But in 1997 the Court ruled that the law could be applied only to the federal government. A number of states then enacted their own versions of it; Mississippi was not among them, until last month.

There is something unsettling about a conception of religious freedom that grants some people exemption from laws that others must obey. Much of the time, opinions about exemption from a particular law mirror the politics of the moment. People who opposed the Vietnam War tended to be sympathetic to devout pacifists who resisted the draft. (In 1971, the Supreme Court affirmed that secular pacifists could be conscientious objectors, too.) Right now, religious freedom seems particularly important to anyone troubled by the spread of gay-rights laws or by the implementation of the A.C.A. But the idea is too big, and too nebulous, to claim any political group as its permanent ally.

Not long ago, Republicans were warning that Sharia law posed a threat to America, which led many states, including Mississippi, to introduce bills that ban the courts from applying “foreign laws.” But during the debate last month in Jackson legislators insisted that “religious freedom” should be interpreted as broadly as possible. State Senator Gary Jackson, a Republican, said, “This law has everything to do with government not interfering with the Buddhist, with the Christian, with the Islamist.” In coming years, that proposition will likely be tested, perhaps by an inmate asking for special meals, or by a Sikh wishing to carry his ceremonial knife through a checkpoint, or by a religious pacifist who wants to resist some new concealed-carry legislation. When politicians talk about religious freedom, broad language often conceals narrower interests. The result is laws that will inevitably be used in ways their proponents can’t predict, and may not like. In Mississippi, as elsewhere, arguments over same-sex marriage and the A.C.A. will eventually give way to general acceptance of a new status quo. But the meaning of “religious freedom” will keep on evolving. ♦