In the case of the Ukraine call, a criminal charge against the president was a far higher legal bar than the Constitution’s “high crimes and misdemeanors” bar for impeachment, which could mean pretty much whatever Congress wants it to mean.

Since the Mueller report was publicly released, Mr. Barr has been involved in the day-to-day work of the department, traveling to United States attorneys’s offices, meeting with local law enforcement and taking part in issues of importance to the White House like gun legislation and the carrying out of the president’s criminal justice reform law. He has also been intimately involved in the inquiry into the death of the accused sex trafficker Jeffrey Epstein.

But Mr. Barr is also closely overseeing a review of the intelligence community’s decision to start a counterintelligence investigation into the Trump campaign during the 2016 election, which is being led by John Durham, the United States attorney in Connecticut. As part of that review, Mr. Durham is exploring what role, if any, a number of countries including Ukraine played in the investigation of the Trump campaign.

“While the attorney general has yet to contact Ukraine in connection with this investigation, certain Ukrainians who are not members of the government have volunteered information to Mr. Durham, which he is evaluating,” Ms. Kupec said.

In the case of the Ukraine call, the Justice Department’s Office of Legal Counsel determined early this month that the whistle-blower complaint should not be shared with Congress’s intelligence committees because it did not flag intelligence-related activities. Rather, it should be referred to the Justice Department as a possible violation of campaign finance law.

Mr. Barr was not involved in the Justice Department’s review, which was overseen by the deputy attorney general, Jeffrey A. Rosen. It was led by the department’s criminal division and conducted by career prosecutors from the division’s public integrity section and the national security division.

Last week, the criminal division concluded that there were no legal grounds for a criminal investigation in to Mr. Trump’s behavior.