Robert Mueller, the special counsel investigating Russian attempts to influence the 2016 presidential election, has taken an interest in a misleading public statement about Donald Trump Jr.'s June 2016 meeting at Trump Tower with a Russian lawyer who claimed to have dirt on Hillary Clinton. In particular, The New York Times reports, Mueller wants to know what role President Trump played in writing the statement, which said the meeting was "primarily" about Russian policy on international adoptions. But neither the meeting nor the statement about it violated the law, which illustrates the difficulty that Mueller will have in demonstrating that the collusion and obstruction perceived by many of the president's opponents actually constitute crimes.

The Trump Tower meeting with Russian lawyer Natalia Veselnitskaya included Paul Manafort, Trump's campaign manager, and his son-in-law, Jared Kushner, as well as his son. When the meeting came to light last summer, the White House scrambled to explain it. "It was a short introductory meeting," said a July 8 statement attributed to Donald Jr. but reportedly crafted mainly by his father. "I asked Jared and Paul to stop by. We primarily discussed a program about the adoption of Russian children that was active and popular with American families years ago and was since ended by the Russian government, but it was not a campaign issue at that time and there was no follow up."

The statement was deliberately misleading, since emails showed that Donald Jr. agreed to meet with Veselnitskaya after one of his father's former Russian business partners, who called her a "Russian government attorney," said she had documents that "would incriminate Hillary and her dealings with Russia and would be very useful to your father." The intermediary described the information as "part of Russia and its government's support for Mr. Trump." Donald Jr.'s reply suggested he was eager to see what Veselnitskaya had. "If it's what you say," he wrote, "I love it." Veselnitskaya, it appears, was bluffing and did not have any useful information.

This episode was embarrassing, but that does not mean it was criminal. When former White House strategist Stephen Bannon called the meeting "treasonous," he was speaking loosely. The legal definition of treason requires waging war against the United States or giving "aid and comfort" to its enemies, defined as nations or organizations with which it is at war.

Donald Jr. did not do either of those things by talking to a Russian lawyer in the hope of obtaining information that could be used against his father's opponent in the presidential election. The fact that Veselnitskaya had ties to the Russian government, which preferred Trump to Clinton, does not transform opposition research into treason. If the meeting with Veselnitskaya provided "aid and comfort" to an enemy of the United States, so did any action aimed at electing Trump. In any case, Russia does not legally qualify as an enemy, since it is not at war with the United States.

Even if the meeting was perfectly legal, lying about it could be a crime. But not in this context. As the Times notes, "Lying to federal investigators is a crime; lying to the news media is not." Even if the elder Trump wrote the statement attributed to his son with the intent of deceiving the press and the public about the motivation for the meeting with Veselnitskaya, that would not be illegal.

Since Trump has agreed to answer questions from Mueller, he still has an opportunity to commit an actual crime by lying about the meeting or about the genesis of the statement attributed to his son. Lying to Mueller would violate 18 USC 1001, which criminalizes deliberately false statements "in any matter within the jurisdiction of the executive, legislative, or judicial branch of the Government of the United States." Michael Flynn, Trump's former national security adviser, pleaded guilty to that offense, as did former Trump campaign adviser George Papadopoulos. Both cases involved lies to the FBI about direct or indirect contacts with Russians—contacts that were not in themselves illegal.

It is still possible, in other words, that Trump will commit a felony by lying about a nonexistent crime. Whether he could be indicted for that offense without being impeached first is a matter of dispute. So is the question of whether the president can obstruct justice by doing things (such as firing the FBI director) that he has the undisputed authority to do. In practice, a president's obstruction of justice, which figured in the impeachments of Richard Nixon and Bill Clinton, is whatever Congress says it is. The current Congress, controlled by the president's party, has little interest in exploring the matter.

No doubt things would be different, as New York Times columnist Bret Stephens argues, if Hillary Clinton had been elected president and proceeded to do what Trump has done. But it seems unlikely that Mueller will change Republicans' minds by focusing on Trump's efforts to mislead the public about his campaign's Russian contacts. If lying to the public were a crime, Trump would be eligible for a life sentence.