"This gets down to, this is a privileged communications only if the conversation was undertaken was the attorney by both of them for the goal of seeking legal advise and the same attorney represented both of them", Painter said.
In September, Trump Jr. told the Senate Judiciary Committee that he, Goldstone and Agalarov "never discussed the meeting again".
The emails from the publicist, Rob Goldstone, were discovered by congressional investigators and raised at Wednesday's classified hearing with Trump Jr., who said he could not recall the interactions, several sources said.
Rep. Adam SchiffAdam Bennett SchiffTrump Jr. set for high-stakes interview with House intel panel Comey back in the spotlight after Flynn makes a deal Schiff: Flynn plea "very significant" MORE (D-Calif.) is challenging Trump Jr.'s reasoning, saying Trump Jr. can not apply attorney-client privilege and "shield" lawmakers from this conversation between father and son just because an attorney was present in the room.
Though neither Trump Jr. nor the president is an attorney, Trump Jr. told the House Intelligence Committee that there was a lawyer in the room during the discussion, according to the committee's top Democrat, Rep. Adam Schiff of California.
An email from Goldstone to senior Trump aide Dan Scavino, now the White House director of social media, reveals a previously undisclosed topic that was discussed at the meeting.
Senator Richard Blumenthal told the committee's chairman, Senator Chuck Grassley, that "cascading disclosures" involving the president's son "suggest collusion between the Trump campaign and Russian officials" during the 2016 election.More news: Devastating winds bring Storm Caroline 'danger' alert
Trump Jr. had gone into the meeting expecting to receive information on Hillary Clinton that would contribute to his father's election victory. In fact, as we learned later, the President himself participated in drafting a statement that made this claim on the way home from a trip to Europe on Air Force One.
As Schiff noted in his statement, it is critical to know exactly what Donald Trump knows about his son's secret meeting with the Russians during the campaign, and what they talked about after it took place. And some legal experts say the White House's involvement could be problematic since there was ongoing criminal probe into Russian meddling.
The question of whether or not the attorney-client privilege applies to a given situation is often a complicated one, but it is also usually a question that courts end up deciding in favor of maintaining the privilege.
In an email, Harvard constitutional law professor Laurence Tribe said he also found Trump Jr.'s invocation of attorney-client privilege to be "ridiculous". If none of the parties are attorneys then there is obviously no privilege.
"Recent revelations have shown beyond question that the American people can only feel certain that Mr. Trump, Jr. has been fully forthcoming if he is subject to a subpoena", Blumenthal wrote to Grassley, The Hill reported. "Who was he representing and what was the goal of this conversation?..." In either case, it could be some time before the matter is resolved while the rest of the investigation moves forward.
Donald Trump Jr. (R) watches his father Republican U.S. presidential candidate Donald Trump leave the stage on the night of the Iowa Caucus in Des Moines, Iowa U.S. February 1, 2016.