WASHINGTON - Today the Supreme Court will hear oral arguments on whether the United States government can detain foreign nationals held at Guantánamo Bay, Cuba, as "enemy combatants" without charge and without hearings. Next week the court will hear arguments in similar cases involving American citizens. Many consider the detention of citizens to be more dubious legally. But from a constitutional standpoint, citizenship should not matter.

All three branches of government have treated citizenship as a central issue. The Bush administration says that it can hold the foreign detainees, most of whom were captured on the battlefield in Afghanistan, without any legal limitations because they are noncitizens held outside American borders. As such, it argues, they have no constitutional rights and no standing in American courts to challenge their detentions.

Fifty years ago, the Supreme Court seemed to adopt a similar view when it upheld the indefinite detentions of a German woman and a Hungarian man at Ellis Island on the basis of secret evidence that they could neither see nor confront. Because they were foreigners who had not been admitted to the United States, the court said, whatever process Congress had provided them was due process. For its part, Congress in 1971 barred executive detention without explicit statutory authorization - but applied the prohibition only to citizens.

These suggestions that noncitizens have less right to be free than citizens are ill advised. Some provisions of the Constitution do explicitly limit their protections to United States citizens - the right to vote and the right to run for Congress or president, for example. The Bill of Rights, however, does not distinguish between citizens and noncitizens. It extends its protections in universal language, to "persons," "people" or "the accused." The framers considered these rights to be God-given natural rights, and God didn't give them only to persons holding American passports.

The human-rights revolution of the last 50 years has similarly identified fundamental rights like the right not to be arbitrarily detained as extending to all regardless of nationality. Human-rights treaties ground these guarantees in "human dignity," and Americans have no monopoly on that.

When one considers the specific right at issue in the enemy combatant cases - the right not to be locked up without a fair process - there is also no good reason to differentiate between citizens and foreigners. From the prisoner's standpoint, every human being has the same interest in not being locked up erroneously or arbitrarily. And from the government's perspective, the security interest in detaining terrorists is the same whether they are citizens or not.

Every person deprived of his liberty under the authority of the United States government should have a right to due process. What process is due may differ depending on the circumstances of detention - whether on the battlefield or far from it. But the nationality of the detainee ought not affect the calculus.

Finally, there is also good practical reason not to distinguish between the basic rights of citizens and foreign nationals. While the federal government has often introduced security initiatives by singling out foreigners, it has just as often sought to extend those tactics to citizens later. The suppression of subversive speech, for example, and race-based detention began as anti-alien measures. But they did not end there.

It used to take years to extend these tactics to American citizens. But things are speeding up. Today the Bush administration will defend its treatment of the Guantánamo detainees on the grounds that they are foreigners who do not deserve American legal protections. Next week, it will argue that it has just as much latitude to detain American citizens. The slippery slope has never been more slick.

David Cole, a professor of law at Georgetown, is the author of "Enemy Aliens: Double Standards and Constitutional Freedoms in the War on Terrorism."