I only have one question:

WASHINGTON — In what may be its most significant religious liberty decision in two decades, the Supreme Court on Wednesday for the first time recognized a “ministerial exception” to employment discrimination laws, saying that churches and other religious groups must be free to choose and dismiss their leaders without government interference.

“The interest of society in the enforcement of employment discrimination statutes is undoubtedly important,” Chief Justice John G. Roberts Jr. wrote in a decision that was surprising in both its sweep and its unanimity. “But so, too, is the interest of religious groups in choosing who will preach their beliefs, teach their faith and carry out their mission.”

The decision gave only limited guidance about how courts should decide who counts as a minister, saying the court was “reluctant to adopt a rigid formula.” Two concurring opinions offered contrasting proposals.

Whatever its precise scope, the ruling will have concrete consequences for countless people employed by religious groups to perform religious work. In addition to ministers, priests, rabbis and other religious leaders, the decision appears to encompass, for instance, at least those teachers in religious schools with formal religious training who are charged with instructing students about religious matters.

Douglas Laycock, a law professor at the University of Virginia who argued the case on behalf of the defendant, a Lutheran school, said the upshot of the ruling was likely to be that “substantial religious instruction is going to be enough.”

Asked about professors at Catholic universities like Notre Dame, Professor Laycock said: “If he teaches theology, he’s covered. If he teaches English or physics or some clearly secular subjects, he is clearly not covered.”

The case, Hosanna-Tabor Church v. Equal Employment Opportunity Commission, No. 10-553, was brought by Cheryl Perich, who had been a teacher at a school in Redford, Mich., that was part of the Lutheran Church-Missouri Synod, the second-largest Lutheran denomination in the United States. Ms. Perich said she was fired for pursuing an employment discrimination claim based on a disability, narcolepsy.

Ms. Perich had taught mostly secular subjects but also taught religion classes and attended chapel with her class.

“It is true that her religious duties consumed only 45 minutes of each workday,” Chief Justice Roberts wrote, “and that the rest of her day was devoted to teaching secular subjects.”

“The issue before us, however, is not one that can be resolved with a stopwatch,” he wrote.

Instead, the court looked to several factors. Ms. Perich was a “called” teacher who had completed religious training and whom the school considered a minister. She was fired, the school said, for violating religious doctrine by pursuing litigation rather than trying to resolve her dispute within the church.

The Rev. Barry W. Lynn, executive director of Americans United for Separation of Church and State, said Wednesday’s decision could have pernicious consequences, by, for instance, barring suits from pastors who are sexually harassed.

“Blatant discrimination is a social evil we have worked hard to eradicate in the United States,” he said in a statement. “I’m afraid the court’s ruling today will make it harder to combat.”

Bishop William E. Lori, chairman of the United States Conference of Catholic Bishops’ ad hoc committee for religious liberty, called the ruling “a great day for the First Amendment.”

“This decision,” he said in a statement, “makes resoundingly clear the historical and constitutional importance of keeping internal church affairs off limits to the government — because whoever chooses the minister chooses the message.”

Chief Justice Roberts devoted several pages of his opinion to a history of religious freedom in Britain and the United States, concluding that an animating principle behind the First Amendment’s religious liberty clauses was to prohibit government interference in the internal affairs of religious groups generally and in their selection of their leaders in particular.

“The Establishment Clause prevents the government from appointing ministers,” he wrote, “and the Free Exercise Clause prevents it from interfering with the freedom of religious groups to select their own.”

The decision was a major victory for a broad range of national religious denominations that had warned that the case was a threat to their First Amendment rights and their autonomy to decide whom to hire and fire. Some religious leaders had said they considered it the most important religious freedom case to go to the Supreme Court in decades.

Many religious groups were outraged when the Obama administration argued in support of Ms. Perich, saying this was evidence that the administration was hostile to historically protected religious liberties.

The administration had told the justices that their analysis of Ms. Perich’s case should be essentially the same whether she had been employed by a church, a labor union, a social club or any other group with free-association rights under the First Amendment. That position received withering criticism when the case was argued in October, and it was soundly rejected in Wednesday’s decision.

“That result is hard to square with the text of the First Amendment itself, which gives special solicitude to the rights of religious organizations,” Chief Justice Roberts wrote. “We cannot accept the remarkable view that the religion clauses have nothing to say about a religious organization’s freedom to select its own ministers.”

Requiring Ms. Perich to be reinstated “would have plainly violated the church’s freedom,” Chief Justice Roberts wrote. And so would awarding her and her lawyers money, he went on, as that “would operate as a penalty on the church for terminating an unwanted minister.”

In a concurrence, Justice Clarence Thomas wrote that the courts should get out of the business of trying to decide who qualifies for the ministerial exception, leaving the determination to religious groups.

“The question whether an employee is a minister is itself religious in nature, and the answer will vary widely,” he wrote. “Judicial attempts to fashion a civil definition of ‘minister’ through a bright-line test or multifactor analysis risk disadvantaging those religious groups whose beliefs, practices and membership are outside of the ‘mainstream’ or unpalatable to some.”

In a second concurrence, Justice Samuel A. Alito Jr., joined by Justice Elena Kagan, wrote that it would be a mistake to focus on ministers, a title he said was generally used by Protestant denominations and “rarely if ever” by Roman Catholics, Jews, Muslims, Hindus or Buddhists. Nor, Justice Alito added, should the concept of ordination be at the center of the analysis.

Rather, he wrote, the exception “should apply to any ‘employee’ who leads a religious organization, conducts worship services or important religious ceremonies or rituals, or serves as a messenger or teacher of its faith.”

At the argument in October, some justices expressed concern that a sweeping ruling would protect religious groups from lawsuits by workers who said they were retaliated against for, say, reporting sexual abuse.

Chief Justice Roberts wrote that Wednesday’s decision left the possibility of criminal prosecution and other protections in place.

“There will be time enough to address the applicability of the exception to other circumstances,” he wrote, “if and when they arise.”