Jeffrey Kahn is a professor of law at Southern Methodist University Dedman School of Law, where his focus is U.S. constitutional law, national security and Russian law.

Bridge of Spies” has all the makings of a great night at the movies: a Steven Spielberg historical thriller, starring Tom Hanks, with a Coen brothers script. Moviegoers can escape for a few hours to a simpler time, before the world went mad with terrorist bombings and medieval beheadings. Before CIA black sites and Guantánamo Bay.

Hanks plays Jim Donovan, a rising lawyer in late 1950s New York City. Donovan finds himself tasked with the pro bono defense of an agent of America’s greatest enemy: a Soviet spy called Rudolf Abel (played by Mark Rylance).

Donovan detests his client’s cause, but intends to give him a zealous defense. “American justice will be on trial,” Donovan’s law partner intones in the film. And Donovan concurs, saying that agreeing to follow the rules of the Constitution is “what makes us Americans. It’s all that makes us Americans.”

Is that what makes us Americans?

That’s a trait sometimes most noticeable by its absence. Respect for the law’s niceties can seem a luxury in times of crisis. The pressure can be intense when the threat seems great and options seem limited. And that is true across time: The Soviets launched Sputnik less than a fortnight before Abel’s trial. A U.S. government newsreel about the case begins with a mushroom cloud.

In 2004, by comparison, Justice Department lawyers questioned the legality of a counterterrorism program that Vice President Dick Cheney’s chief of staff felt essential to national security. “If you rule that way,” one of the lawyers recalls in the intense response, “the blood of the hundred thousand people who die in the next attack will be on your hands.” Despite our great American tradition of “a government of laws, not of men,” our history reveals the difficulties we repeatedly encounter living up to that high standard in times of perceived national crisis.

The true-life story Spielberg adapts for the screen is a history lesson we need now more than ever. Life wasn’t simpler in Donovan’s day. In fact, the essential questions in the rules-bending fight against Cold War spies are surprisingly similar to the constitutional corners cut today in the search for terrorists hidden among us.

The movie is based on the sensational arrest of Abel, a KGB colonel. As I discovered preparing to speak about the case at an international conference held (ironically enough) in Moscow and noted in a subsequent law review article, Abel was the Soviet Union’s top spy in North America. FBI agents pushed their way into his hotel room in Manhattan on June 21, 1957. He was caught red-handed (so to speak), with the tools of his trade all around him, including microfilm and a cipher pad. The FBI had already uncovered a hollowed-out nickel used to transport coded messages.

The FBI wanted Abel to turn double-agent against his Soviet masters. So publicity about his capture was the last thing they wanted. But that presented a problem. Public appearance before a judge is required shortly after any arrest. An opportunity must be given to retain counsel. The media and public are welcome in an open courtroom.

To avoid all that, the FBI turned to Immigration and Naturalization Service officials to pick up Abel on a pretextual violation while federal agents waited to search his vacated room. Instead of pursuing the normal route — a deportation hearing in New York — Abel was spirited far away.

There was no public appearance before a magistrate. No charge. No lawyer. In the words of Justice William Brennan, dissenting from the Supreme Court opinion that ultimately resolved the case, “As far as the world knew, he had vanished.”

After his capture in Manhattan, a special plane waiting in New Jersey flew him 13 hours and 2,000 miles away to McAllen, Tex. For almost seven weeks, the FBI (not immigration officials) engaged in “conveyor belt” interrogation (i.e., federal agents questioning Abel in shifts) aimed either to turn Abel or break him.

But the FBI misjudged its quarry. Abel would not turn, and for the most part, wouldn’t even speak. Finally, the FBI gave up its dream of a double agent and rushed Abel through the deportation process (for which he finally received a lawyer), but still didn’t deport him. Instead, authorities returned him to New York to face a capital charge of atomic espionage. They relied on the evidence acquired during Abel’s pretextual seizure to seek a conviction for espionage.

And that’s where Donovan comes in with his zeal for American justice and following rules. Who would think Abel’s arrest, secret detention and lawyerless interrogation for a hot summer in south Texas would be possible in the constitutional confines of the American criminal justice system?

Donovan invoked the Fourth Amendment to the Constitution, which generally requires a warrant from a judge for arrests and searches, and does not allow secret disappearances on the say-so of government agents (though the practice would have been quite familiar to a Soviet spy trained in Stalin’s Russia).

Donovan lost his case, though. Abel was convicted, and the Supreme Court (although it took two rounds of oral argument) upheld the conviction by a slim margin. Donovan more successfully persuaded the court not to sentence Abel to death. That led to Abel’s trade Feb. 10, 1962, on the Glienicke Bridge — the “bridge of spies” — connecting West Berlin to East Germany.

Spielberg’s movie ends on a high note. But comparison with contemporary counterterrorism efforts reveal a more disturbing reality. Pretextual arrests have the imprimatur of the Supreme Court, a holding reinforced by later opinions. In the early days of the so-called “war on terror,” the Department of Justice used immigration arrests no different than Abel’s to seize and detain 762 people, though not a single one was even charged with a terrorism-related crime.

Transparency suffered, too, in the war on terror. At roughly the same time, the U.S. Chief Immigration Judge ordered the closure of “special interest” immigration hearings that kept those held on that pretext away from the public eye. The courts divided on the constitutionality of this action, a circuit split the Supreme Court left unresolved.

The fate of lawyers defending such unpopular clients hasn’t changed much, either. Donovan was subjected to harsh personal attacks at the time, and probably sacrificed a bright political career despite his subsequent rise, by accepting the professional obligation to provide good counsel to Abel. In 2007, a Department of Defense official similarly attacked the attorneys who provided counsel to detainees at Guantánamo Bay.

American law, and American lawyers, do have a proud history of defending the rule of law that, as Spielberg’s Donovan says, is “what makes us Americans.” Their names occupy a proud place alongside that of Jim Donovan. John Adams defended British soldiers on trial for the Boston Massacre. Kenneth Royall defied Franklin Delano Roosevelt to seek judicial review before the Supreme Court for Nazi saboteurs subjected to rushed trials before military commissions. More recently, Charles Swift defended the right of Guantánamo detainees to fair hearings and the writ of habeas corpus.

The temptation to bend the rules is timeless. Just like the struggle of the best lawyers to resist that temptation. What makes us Americans is the open nature of that constant struggle.

CORRECTION: An earlier version of this story attributed a line in “Bridge of Spies” to the wrong character. “American justice will be on trial” is said by Jim Donovan’s law partner, not by Donovan.