OPINION: Comey didn’t commit a crime — neither did Donald Jr.

Now it is President Trump who is accusing his political enemies of illegal behavior. He accused former FBI Director James Comey of leaking classified material when he surreptitiously gave a law professor friend a memo he wrote about his meeting with the president. Comey told the professor to leak the memo to the media in an effort to pressure Deputy Attorney General Rod Rosenstein to appoint a special counsel to investigate Trump. The president tweeted that this is “so illegal.”

{mosads}So now the shoe is truly on the other foot. Trump’s political enemies have accused the president of engaging in illegal behavior, including obstruction of justice, witness tampering, extortion, even treason. And now it is President Trump who is accusing Comey of illegal behavior.

But turnabout is not fair play. Both sides are wrong in trying to expand existing criminal laws to cover the questionable conduct of their political opponents. This is a dangerous disease that has been infecting the body politic for several years now. Each side is quick to accuse the other not only of political sins, but of actual crimes, based on dubious evidence and improper, if not unconstitutional, expansion of criminal statutes to target political opponents.

James Comey leaked CLASSIFIED INFORMATION to the media. That is so illegal!

— Donald J. Trump (@realDonaldTrump) July 10, 2017

Not to be outdone by President Trump, a former ethics lawyer for President George W. Bush, has accused Donald Trump, Jr., of treason — yes, treason — for meeting with a Russian lawyer during the campaign in an alleged effort to obtain negative information about Hillary Clinton. This is what Richard Painter, Bush’s ethics lawyer, said on MSNBC: “We do not get our opposition research from spies, we do not collaborate with Russian spies, unless we want to be accused of treason.” He said that if the story is true, those who met with the Russian lawyer should be “in custody by now.”

But even if these allegations are true, this does not even come close to the legal definition of treason. The crime of treason is explicitly defined in the Constitution as limited to the following conduct: “Treason against the United States shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort.” (Emphasis added.) It does not include receiving aid from a Russian lawyer, whether that lawyer was acting in a private capacity or as a surrogate for her government.

This is treason. He must have known that the only way Russia would get such information was by spying.https://t.co/MSwr3DsbHs

— Richard W. Painter (@RWPUSA) July 9, 2017

Painter’s accusation is all too typical of the charges flying around from both sides of the political spectrum. Each side stretches the meaning of statutory and constitutional language to suit their partisan needs, without regard to the civil liberties implications of giving prosecutors the untrammeled power to retroactively fit the often elastic words of criminal statutes to actions that were not deemed criminal at the time they occurred.

Republicans tried to do that with Clinton by stretching the word “espionage” to cover her improper but innocent use of home computer system to send and receive emails. Comey got it right when he declined to prosecute her, saying that nobody had previously been prosecuted for comparable conduct. He then went on the criticize her — a decision that many regarded as beyond the scope of his authority.

But his critical words directed against Clinton may now come back to haunt him because if it is true that he leaked classified material, he too, is subject to the kind of criticism he leveled at Clinton. But he, too, should not be prosecuted for leaking the material, based on the evidence that we now know.

If the allegations against Comey and President Trump’s son are true, they should both be criticized for what they did. It is unseemly, at the very least, for a former director of the FBI to launder potentially classified material through a law professor in order to get it to the media. It was also cowardly for Comey to use this indirect method to seek the appointment of a special counsel. He can be rightly criticized for failing openly to seek the appointment of a special counsel. But his conduct does not seem to rise to the level of illegality, notwithstanding President Trump’s hasty tweet.

The same can be said about President Trump’s son meeting with the Russian lawyer if the object of the meeting was to obtain negative material about Hillary Clinton. There would be nothing illegal about any such a discussion, even if it did occur, but it would certainly be subject to political criticism.

When non-criminal conduct that is deserving of political criticism is investigated as criminal, both sides lose. Even more importantly, all Americans lose important civil liberties protections guaranteed by our Constitution.

Alan M. Dershowitz is the Felix Frankfurter Professor of Law, Emeritus, at Harvard Law School and author of Taking the Stand: My Life in the Law and Electile Dysfunction: A Guide for the Unaroused Voter. Follow him on Twitter @AlanDersh or Facebook @AlanMDershowitz.

The views expressed by contributors are their own and are not the views of The Hill.