Can the Defense Department overrule the U.S. Supreme Court? Can the Boy Scouts of America? The short answer is: Of course not. But a full response turns out to be more complicated, and it offers a lesson for thinking about the relationship between constitutional law and the evolving nature of rights.

Here’s the lesson. We often think that our rights are established by the Constitution and by the Supreme Court, interpreting that document. True, the Constitution is fundamental, but some of our most important rights, as we understand and live them, are a product of changing social values, which affect private institutions, public officials and sometimes even constitutional law.

We are now witnessing two compelling examples: the recent decision of the Defense Department to allow women to serve in combat, and the Boy Scouts’ announcement that it will reconsider (perhaps as early as this week) its longstanding national ban on gay members.

Let’s begin with a little history. In a 1981 decision, Rostker v. Goldberg, a divided Supreme Court resolved one of the most controversial sex-discrimination cases in the nation’s history. The constitutional question was whether the federal government could refuse to register women for the draft.

The government defended male-only registration with a breathtakingly simple argument: The primary purpose of registration was to ensure that people would be available for combat, which was limited to men by law. In the government’s view, registration of women would have no point.

Remarkably, those who challenged the law raised no objection to the exclusion of women from combat. They took that form of discrimination as a given. They merely contended that thousands of registrants, if called up for military service, would end up working in noncombat positions. They insisted that to avoid unconstitutional sex discrimination, the government should register men and women alike ― while also using only men in combat.

By a vote of 6-to-3, the court sided with the government. The court said that judges owed special deference to the views of the military. It concluded that because the government wanted the overwhelming majority of registrants to be available for combat, it could refuse to register women.

In its 2000 decision in Boy Scouts of America v. Dale, a divided Supreme Court resolved one of the most controversial freedom-of-association cases in the nation’s history. New Jersey had enacted a law forbidding discrimination on the basis of sexual orientation in public accommodations. The New Jersey Supreme Court concluded that this law applied to the Boy Scouts, who asked the Supreme Court to rule that New Jersey was violating its right of association.

By a vote of 5-to-4, the court agreed with the Boy Scouts. It emphasized that the Boy Scouts believed that “homosexual conduct is not morally straight,” and did “not want to promote homosexual conduct as a legitimate form of behavior.” According to the court’s majority, New Jersey was striking at the heart of the Scouts’ deepest moral commitments.

In 1981 many people would have been astonished to hear that in a little more than three decades, and without the slightest pressure from the Supreme Court, the Defense Department would allow women to serve in combat. Yet on Jan. 24 of this year, the Pentagon announced, with the full support of the Joint Chiefs of Staff, that the military is lifting its longstanding prohibition on women in combat.

As recently as 2000, many people would have found it unimaginable that in a little more than a decade, the Boy Scouts would seriously consider eliminating its ban against the admission of openly gay members. Yet on Jan. 28 of this year, the Boy Scouts announced that it will re-evaluate its longstanding prohibition and decide whether to allow local troops to admit gay members.

True, the Boy Scouts’ decision has yet to be made, but the very fact that it is reconsidering its prohibition attests to the mounting consensus against discrimination on the basis of sexual orientation.

The broader lesson is that social movements and evolving social values are responsible for many rights that Americans now take for granted. The right to be free from sex discrimination has become entrenched, but it did not really emerge until the last third of the 20th century.

The individual right to own guns was a settled part of American culture long before it was a settled part of constitutional law; indeed, the Supreme Court didn’t explicitly recognize that right until its 2008 decision in District of Columbia v. Heller.

To a remarkable extent, disability rights have become broadly accepted, as reflected in bipartisan support for the Americans With Disabilities Amendments Act of 2008 (passed by unanimous consent in both the Senate and the House of Representatives). But the nation’s acceptance of disability rights has nothing to do with constitutional law and everything to do with changing social understandings.

Powerful though they are, the Defense Department and the Boy Scouts of America have no authority to overrule the Supreme Court. But it is an enduring feature of our constitutional system that as they learn over time, public and private institutions are free to endorse understandings of rights that go beyond anything announced by the highest court in the land. 

By Cass R. Sunstein

Cass R. Sunstein, the Felix Frankfurter professor of law at Harvard University, is a Bloomberg View columnist. He is the co-author of “Nudge” and author of “Simpler: The Future of Government,” forthcoming in 2013. The opinions expressed are his own. ― Ed.