Ryan Goodman is a professor at New York University School of Law, a member of the State Department’s Advisory Committee on International Law and co-editor in chief of Just Security. He was a special counsel to the general counsel of the Defense Department from 2015 to 2016.

A major question remains as to whether President Trump’s inner circle violated federal law before coming into office by communicating with foreign governments and undermining the official policies of President Barack Obama. But if you listen to almost any recent commentary, you would think that the law in question — 1799’s Logan Act — is essentially a dead letter. Why? We’re told that no one has been convicted of violating the Logan Act since the law was signed more than 200 years ago.

That’s true, but that’s not nearly the end of the argument. What commentators miss is that the Logan Act has been “enforced” and relied upon time and again by the executive branch, most notably through the State Department.

In the 19th century, secretaries of state kicked foreign ambassadors out of the country for aiding and abetting violations of the Logan Act. The Spanish minister to the United States in 1805 and the British consul during the Civil War were expelled on that basis. (It is fair to wonder if the current Russian ambassador — Sergey Kislyak — should meet a similar fate for his conversations with ousted national security adviser Michael Flynn before Trump’s inauguration.)

(Sarah Parnass/The Washington Post)

During periods of tension with foreign governments, the State Department restricted — and sometimes suspended — U.S. passports out of concern for Logan Act violations. President Woodrow Wilson’s secretary of state invoked the Logan Act in denying passports to U.S. delegates to the Stockholm Peace Conference in 1917. In 1944, Secretary of State Cordell Hull advised President Franklin D. Roosevelt to include explicit conditions in the issuance of passports to a prominent professor and religious leader to travel to the Soviet Union “particularly in view of possible repercussions which may arise under the ‘Logan Act.’ ”

In 1966, the State Department confiscated the passports of Americans who had traveled to Vietnam to broker a peace agreement. In 1970, the State Department included the full text and summary of the Logan Act’s history in a digest of U.S. practices dictating that foreign diplomatic correspondence be directed through the department. In 1975, the State Department issued an opinion explaining why the trip by a pair of congressmen to Cuba met the specific conditions of the Logan Act in terms that, as then-Rep. Newt Gingrich (R-Ga.) would later say, “would imply that the Logan Act is alive, valid.”

It is no wonder that in 2001, the nonpartisan Congressional Research Service, in a report prepared for the Senate Foreign Relations Committee, described the utility of the Logan Act as appearing “to have strengthened executive branch control over negotiations” with foreign countries by restricting the actions of unauthorized citizens.

Presidents themselves have also invoked the law. In 1968, President Lyndon Johnson believed Richard Nixon violated the Logan Act during Nixon’s presidential campaign by attempting to send an intermediary to tell South Vietnam to hold off on a peace agreement until after the election. Having wiretapped that conversation (sound familiar?), Johnson informed Vice President Hubert Humphrey — Nixon’s opponent in the campaign — but Humphrey decided not to do anything about it. He feared the revelation would unfurl a “constitutional crisis” if Nixon won the election a few days later.

And in 1988, President Ronald Reagan publicly cautioned presidential candidate Jesse Jackson against traveling to Moscow to seek the release of Soviet dissident Andrei Sakharov. Reagan remarked: “It is a case that there is a law, the Logan Act, with regard to unauthorized personnel, civilians, simply going to — or citizens — to other countries and, in effect, negotiating with foreign governments. Now that is the law of the land.”

Congress, for its part, has indirectly affirmed the Logan Act over the years. In the late 1970s, Sen. Edward Kennedy (D-Mass.) attempted to repeal the act but was rebuffed by Sen. James Allen (D-Ala.), who argued, “I do not believe we need to have millions of secretaries of state running about carrying on foreign negotiations with foreign governments.” In 1980, the Logan Act had been dropped from a draft revision of the Criminal Code, but Sen. Bob Dole (R-Kan.) promised to amend the bill, saying: “It is the law of the land, it is on the books, and it should be enforced.” And in 2006, the House Ethics Committee warned departing members of the statutory restrictions of the Logan Act. Acknowledging that nobody in living memory had been prosecuted under the act, the committee nevertheless instructed “the law remains on the books.”

These episodes do not exhaust — by any stretch — the long career of the Logan Act, which has also found its way into successful courts-martial and advice of the judge advocate of the armed services. The true history of the law should worry the Trump administration. If the public becomes aware of how much our government has relied upon the Logan Act, it will raise the temperature of the hot water these individuals are already in.