By Chris Edelson

Donald Trump clearly has a way of grabbing attention by making bold statements that energize his supporters and repel his critics.

After the terrorist attacks in Paris last November, Trump initially said he "would certainly implement" a database to register and track Muslims in the United States, while further suggesting there should be surveillance of mosques. He also left open the possibility that Muslim Americans might be required to carry specific identification indicating their religious faith.

Critics observed that these ideas bore an uncomfortable resemblance to practices associated with authoritarian regimes - the identification scheme, in particular, was compared to the yellow star Jews were forced to wear by the Nazis. Trump backed off a bit, saying his database would apply only to refugees from Syria and that he wanted surveillance only of "certain mosques."

A few weeks later, his campaign issued a statement declaring that "Donald J. Trump is calling for a total and complete shutdown of Muslims entering the United States until our country's representatives can figure out what is going on." The press often describes this as a proposed "temporary" ban, but it is hard to define the circumstances that would result in Trump's proposed immigration ban being lifted.

It can be similarly difficult to understand precisely what Trump has in mind.

Last month, Trump confusingly said that the ban on immigration by Muslims "hasn't been called for yet" (notwithstanding his very clear public statement last year) and was "just a suggestion until we find out what's going on." In fact, he said, since he's "not the president, everything [he has said] is a suggestion." He later added, "I'm always flexible on issues."

It's worth noting, however, that a central part of Trump's campaign message is his effort to project himself as a "strongman" type who will make the kind of tough decisions needed to keep the United States safe, decisions that weaker leaders fail to make.

When he first mentioned registering Muslims and was asked how this would be done, Trump's response was, "It's all about management. . . . Our country has no management." In contrast, Trump said of Vladimir Putin, Russia's autocratic president: "He's running his country and at least he's a leader, unlike what we have in this country."

This is the distilled essence of Trump's own campaign, which, as foreign-policy commentator Robert Kagan recently observed, is not about specific policy proposals but rather "an attitude, an aura of crude strength and machismo, a boasting disrespect for the niceties of the democratic culture that he claims, and his followers believe, has produced national weakness and incompetence."

Fine, you might say, but there's no way Trump could implement any of these radical proposals, assuming he is elected president and they graduate from "suggestions" to policy initiatives. Surely the U.S. Constitution would prevent these nakedly discriminatory practices - singling out a group of Americans based on their faith, while barring foreign Muslims from even entering the country. In theory, that is correct (most clearly for Americans, less obviously for foreigners).

The Constitution contains potentially powerful limits on power as well as protections against discrimination. In our system, the president is not a king. He or she is subject to the rule of law, and the Constitution stands as a bar against arbitrary discrimination based on religion. In fact, religion is the very first freedom protected in the Bill of Rights.

But the Constitution is not self-enforcing: It requires each branch of government to do its part - as well as ordinary Americans, whom James Madison identified as the primary check on government overreach.

There are dark chapters in American history when presidents exceeded their constitutional power and violated Americans' rights. President Franklin D. Roosevelt issued an order leading to the internment of more than 100,000 Japanese Americans in prison camps during World War II. The Constitution provides no power for the president to do this and contains specific provisions prohibiting such discrimination. But during wartime, Congress and the Supreme Court ratified this action.

If Trump, or any president, follows in this sad tradition, it will be up to the rest of us to say whether it is legitimate.

Chris Edelson, an assistant professor of government at American University's School of Public Affairs, is the author of "Power Without Constraint: The Post-9/11 Presidency and National Security" (University of Wisconsin Press, May). edelson@american.edu