Thirty years ago today, on December 8, 1981, the Supreme Court decided the case of Widmar v. Vincent—probably the most important pro-religious-liberty judicial decision of the modern era. The question at issue was whether the University of Missouri-Kansas City (UMKC), a state university, could bar a Christian student group named “Cornerstone” from using university facilities because the students wished to engage in religious worship and expression. While UMKC allowed other student groups to use its facilities, the university excluded Cornerstone from doing so under a regulation forbidding the use of its buildings “for purposes of religious worship or religious teaching.”

By a vote of 8–1, the Court held that the First Amendment’s Free Speech Clause protects religious speech and association by private speakers and groups, just as it protects speech by any other speakers on any other subject, and that the Establishment Clause does not authorize discriminatory exclusion of religious speech.

This was a signal ruling. The free-speech holding was hardly new to Widmar—many of the Court’s great free-speech cases of the 1930s, 1940s, and 1950s involved religious expression—but the Widmar case framed the issue clearly and stated the rule simply. The decision came at a moment in the Court’s history when the principle of free religious speech had become endangered by the encroachment of overreaching claims of church-state “separation,” claims that many took to suggest that religion must be affirmatively excluded from the public sphere and from public discourse. Certainly UMKC (and its lawyers) thought that religious speech, by private parties, must be kept off university grounds. Separation of church and state required exclusion of religious speech, they supposed. UMKC’s posture was not so much one of hostility to religion as one of ignorance about the First Amendment—though the consequence was much the same.

Widmar marked a decisive turning point. Of course, the disposition to suppress private religious expression—to exclude, to hamper, to discriminate—persists even today. But Widmar (with its many successor cases) stands firmly in the way of the view that such suppression is in any way justified, let alone required, by the Constitution. Widmar repudiated such First Amendment ignorance.

Here is what the Court held in Widmar: Freedom of speech forbids government from prohibiting, punishing, or penalizing speech based on its content. This was already an oft-stated principle. The Free Speech Clause of the First Amendment thus forbids government from excluding religious speakers and groups from forums for expression—or from any other benefit—on account of the religious content of their expression or the religious nature of their views or association. Furthermore, the Court went on to hold, the Establishment Clause of the First Amendment, so often unthinkingly invoked to wall off religion from the public sphere, emphatically does not authorize or justify discriminatory exclusion of private religious speakers and groups from public forums for expression, or from other public benefits.

While there are many important cases in the Supreme Court’s First Amendment oeuvre, none in the last thirty years captures as succinctly and correctly as Widmar so many basic, important principles of the freedom of speech and, by implication, the American freedom of religion generally. Few principles of the freedom of speech are more foundational or of greater practical importance to religious liberty than the proposition that religious speech is as fully protected as speech on any other subject: Religious speech, association, or identity can no more serve as the basis of exclusion from a public forum or a public benefit than can any other viewpoint or affiliation. Religious freedom might mean more but cannot mean less than full and equal inclusion in the public sphere and the right to share in First Amendment freedoms of expression and association.

Widmar’s free-speech holding is thus fundamental to the freedom of religion. It is the basis for the right of evangelism: Freedom of religious expression, and the equal status of religious ideas, keep government from suppressing religious discourse and debate. And Widmar’s free-speech principle is closely allied with the freedom to exercise one’s religious convictions in society generally: It is the principle that proclaims the equal status of religious views, religious arguments, religiously motivated actions, religious associations, and religious identity in American public life. Freedom of religion means, at bedrock, the right of religious persons, groups, and ideas to participate fully and equally in the life of the community and in the marketplace of ideas.

Nearly as important as Widmar’s embrace of the affirmative right to religious expression is its rejection of the mischievous notion that the Establishment Clause, which forbids government “establishment of religion,” somehow mandates, or justifies, government discrimination against religion. The Establishment Clause’s original meaning was to forbid official coercion in matters of religion, whether by direct state compulsion or by conditioning benefits or privileges on a citizen’s engaging in religious conduct favored by government. (That is the principle that makes the Court’s decisions of the 1960s striking down public-school official prayer exercises correct: Such practices employ the coercive machinery of the state to get schoolchildren to pray the government’s prayer.)

Unfortunately, a series of cases in the 1970s involving various state government programs of direct aid to private, parochial religious schools led the Court to devise a confusing “three-pronged test” intended to identify improper government sponsorship of religion. Like so many judicial interpolations into the constitutional text, however, the “Lemon test,” named for the 1971 case of Lemon v. Kurtzman that first used it, led the Court far astray. Soon, the Court’s decisions had transformed the Establishment Clause from a rule forbidding government coercion of religious practice into something approaching a rule requiring government exclusion of religion from the public square or from generally available benefits.

Widmar rejected such an understanding. Although the eight-member majority worked within the framework of the ‘70s’ Lemon test, it made clear that a policy of equal inclusion of religion does not violate the Establishment Clause. Equal inclusion has neither the purpose nor the effect of special state promotion of religion. It also avoids church-state tangles: A rule that required government to ferret out and exclude religious expression not only would violate core free-speech principles—Widmar’s free-speech holding—but also would entangle government terribly in matters of religion, in violation of religious freedom principles of church-state separation.

Widmar thus broke the Establishment Clause logjam that had become a barrier to true religious freedom. The former skewed thinking—that separation required discrimination—began to give way. Much as Brown v. Board of Education had broken the back of separate-but-equal state racial segregation a generation earlier, Widmar broke the back of separate-and-unequal official religious discrimination. Within a few years of Widmar, the Court held that tax arrangements providing neutral aid to families choosing private religious schools, rather than direct aid to the schools themselves, posed no special problem under the Establishment Clause (Mueller v. Allen, 1983). Decisions followed rejecting the idea that the Establishment Clause forbade vocational education benefit programs from being used for religious education (Witters v. Washington Department of Services for the Blind, 1986), or that disability services or remedial education could not be provided to children attending religious schools (Zobrest v. Catalina Foothills, 1993; Agostini v. Felton, 1997).

Widmar’s “equal access” rule was enacted by Congress in 1984 as a requirement for public secondary schools receiving federal financial assistance, in the important “Equal Access Act,” and was upheld by the Supreme Court against Establishment Clause challenges (Westside Board of Education v. Mergens, 1990): this means that high-school and middle-school religious student groups may form and meet on public school premises. The Court likewise applied the rule of Widmar to religious groups seeking to use or rent public-school building facilities after hours or on weekends, on an equal basis with other community groups (Lamb’s Chapel v. Center Moriches Union Free School District, 1993), and to after-hours religious clubs for children at elementary schools (Good News Club v. Milford Union Free School District, 2001). Religious worship, religious expression, and even child evangelism programs could take place on public school grounds, under equal-access principles.

In a dramatic and important extension of Widmar, the Court in 1995 held that student religious groups at state universities were entitled to equal access to student-activities funding by the university and that the Establishment Clause posed no barrier to such equal access. Thus, the University of Virginia was forbidden from denying funding to an evangelistic Christian student newspaper simply because of its religious content and viewpoint (Rosenberger v. Rector and Visitors of University of Virginia, 1995). Funding, the Court held, could be every bit as much a “forum,” from which student religious groups could not be excluded based on the content of their expression, as access to use of university buildings for religious meetings, worship, prayer, and Bible study. Given Rosenberger, it became a cinch that school-choice “voucher” plans that allowed parents to choose religious schools would be upheld against Establishment Clause challenge; and they were, in Zelman v. Simmons-Harris, in 2002. Widmar’s principle—that neutral inclusion does not violate the Establishment Clause—controlled.

These are significant results, with hugely positive consequences for religious freedom and equality in American public life. They would have been unthinkable had Widmar gone the other way, thirty years ago.

Of course, there has been some backsliding through isolated decisions in tension with Widmar’s reasoning. For example, Locke v. Davey (2004) held, somewhat bizarrely, that a state scholarship program to help lower-income, high-performing high-school students attend public or private college could exclude students choosing programs in theology. The Court emphasized, consistent with Widmar—and with Witters, Zobrest, and Rosenberger—that such exclusion was in no way constitutionally required.  Yet Locke’s  holding that such exclusion is permitted is hard to square with Widmar and cases following it.  More recently, and even more bizarrely, the Court in Christian Legal Society v. Martinez (2010) held that a state university could insist that student religious groups not have religious-belief requirements for their members and leaders. Taken seriously, Martinez is hard to square with Widmar’s premise that religious groups may not be discriminated against because of their religious nature.

But given Widmar, these isolated decisions ought not have legs. Locke v. Davey now appears to be a blip or a hiccup, limited to its facts and (one hopes) destined to be overruled in a proper case. And CLS v. Martinez may be limited to its oddly hypothetical, unreal stipulated facts (insisting that all student groups allow all people—regardless of whether they share the aims of the group—access to leadership roles).

Despite exceptions and odd departures, Widmar states the bedrock rules: The Free Speech Clause forbids government from excluding or discriminating against private parties’ religious expression because of its religious content. The Establishment Clause does not authorize or justify such discrimination, ever. Where government has provided a program or a benefit on a general basis, it may not exclude religious persons or groups on the basis of their religious expression or identity. It is hard to think of a better, more succinct statement of the essentials of religious freedom.