By Joan Biskupic

CNN Legal Analyst and Supreme Court Biographer

Newly released emails related to Donald Trump Jr.'s June 2016 meeting with a Russian lawyer to gather damaging information on Democratic presidential nominee Hillary Clinton ratchet up the possible legal liability for the President's son and other campaign operatives involved with the Russians last year.

The latest emails could relate most directly to federal campaign finance law barring the solicitation of any contribution or "thing of value" from foreign nationals.

Legal analysts also raise the possibility of perjury, for example, if Trump Jr. or anyone else involved earlier denied any Russian meeting to federal investigators. Anyone who made a false statement to federal investigators about the meeting, including a material omission on government personnel paperwork, could be in serious jeopardy. It is not clear that he has made any statements under oath related to the Russian interference in the election.

Some other critics of the administration, including Sen. Tim Kaine, a Virginia Democrat who was Clinton's running mate, have suggested the President's son might have engaged in treason by dealing with a foreign adversary -- but that is a possibility that many legal analysts reject.

Both Constitution and federal law covering treason provide the United States be actively at war with the foreign adversary for such a charge.

The New York Times first reported on Saturday the meeting between Trump Jr. and a Russian lawyer. Trump's son Tuesday released a chain of emails about the meeting with someone the email said was a Kremlin-connected lawyer who supposedly had "very high level and sensitive information" that would "incriminate" Clinton.

That email from publicist Rob Goldstone offered a meeting with "a Russian government attorney" with "some official documents and information that would incriminate Hillary and her dealings with Russia."

Trump Jr. responded: "If it's what you say I love it."

Federal campaign finance law makes it a crime to "knowingly solicit, accept, or receive from a foreign national any contribution or donation ... or other thing of value."

The crucial question of any prosecution would involve whether the information exchanged rises to a "thing of value," said CNN legal analyst Stephen Vladeck.

"Whether the Trump campaign violated campaign finance laws simply by having the meeting is actually a bit complicated," said Vladeck, "a University of Texas law professor, because it turns to some degree on the extent to which the opposition research is a 'thing of value,' and whether the Russians thereby gave 'substantial assistance' to the campaign, terms that are notoriously opaque in this context."

He added that for federal investigators, the larger issue could be whether laws were broken in subsequent misstatements or refusals to acknowledge the existence of the meeting.

Richard Hasen, a University of California, Irvine, law professor who specializes in election law, said Tuesday's disclosures could ramp up the legal consequences. He said the emails suggest the President's son knew he would be meeting with a foreign source for potentially valuable information.

He cautioned, however, that such campaign violations can be difficult to prove.

"The email, if accurate," Hasen said, "seems to show knowledge (of the Russian government connection) but we don't know if the email is accurate or there is more. There is also the legal issue as to whether this promise of dirt from the Russian government can be a 'thing of value' for purposes of the law."

Hasen said earlier Federal Election Commission guidance would suggest such opposition research would be covered, but that he was not aware of any prosecutions that would be relevant to the new Trump controversy.

Sen. Kaine said Tuesday that the latest revelations about Trump Jr. meant that the investigation should move toward "even potentially treason."

Richard Painter, one of the top ethics lawyers during President George W. Bush's administration, has offered a similar assessment, including by tweeting on Sunday: "This is treason. He must have known that the only way Russia would get such information was by spying."

But other analysts say such a charge would require that the US and Russia actually be at war.

"I think it's absurd to call it treason," sad CNN senior legal analyst Jeffrey Toobin, who has previously argued that Trump's alleged efforts to influence former FBI Director James Comey likely amounted to obstruction of justice.

Carlton F.W. Larson, a constitutional law professor at the University of California at Davis who has extensively studied treason laws, has previously cast doubts on the treason angle. In February, he wrote that it was a "myth" that aiding Russia is treason. Part of the difficulty, he argued, is that treason laws specifically are designed to guard against aiding "enemies" of the United States. That's defined as countries with which the United States is at war, and the US is not currently at war with Russia.

CNN's Marshall Cohen contributed to this report.