At least three Democrats were among roughly 50 House Members who attended a constitutional training session Monday with Supreme Court Justice Antonin Scalia.

All House Members were invited to attend the first in a series of closed-door training sessions organized by the Tea Party Caucus and its founder, Rep. Michele Bachmann (R-Minn.).

The event was originally billed as a training session for GOP freshmen. Bachmann said she later invited Members of both parties and of any seniority because her “opinion is that the Constitution is not a partisan document, it’s an American document.”

Democratic Reps. Jan Schakowsky (Ill.), Jerrold Nadler (N.Y.) and Mel Watt (N.C.) took Bachmann up on the offer. “We are pleased that this truly was a bipartisan seminar,” Bachmann said. “Everyone was very respectful.”

Liberal groups have criticized Scalia, a conservative justice, for participating in the event. Lawmakers who attended said that he spoke about complex legal issues and that the session was more academic than political. The new health care overhaul law, which Republicans have attacked as unconstitutional, did not come up, according to the lawmakers.

Schakowsky said Scalia did give examples of “old cases where the Congress made mistakes, he felt, in its judgment.”

She added, “But they were not especially of a political nature and not particularly, as I could see, relevant to some of the things that are going on today.”

Scalia discussed the Constitution “in a very intellectual and legal framework,” and his comments “were perfectly suited for a bipartisan audience,” Schakowsky said. Scalia suggested that all Members obtain a hard copy of the Federalist Papers and “underline and dog-ear” important portions, she added.

Freshman Rep. David Schweikert said Scalia spoke about lawmakers’ obligation to honor the Constitution and reminded them about their oath of office.

“You could actually see a number of the heads in the room all nodding up and down, understanding in many ways when it comes to legislation moving, we are the first pass … at making sure it’s constitutional,” the Arizona Republican said.

Bachmann said she would like to invite other Supreme Court justices and legal scholars to headline future seminars. Larry Arnn, the president of Hillsdale College in Michigan, is slated to speak to interested lawmakers next week.