WASHINGTON – A federal appeals court judge is under fire from critics who say his comments last week about President Bush’s legitimacy amount to a breach of judicial ethics.

Speaking to a liberal lawyers group on Saturday, Judge Guido Calabresi of the 2nd Circuit Court of Appeals compared President Bush’s rise to power to the ascendance of dictators such as Hitler and Mussolini.

In comments first reported Monday by The New York Sun, the judge called the Supreme Court’s decision resolving the election in favor of Mr. Bush “illegitimate” and appeared to exhort voters to toss the president out of office.

“When somebody has come in that way, they sometimes have tried not to exercise much power. In this case, like Mussolini, he has exercised extraordinary power,” Judge Calabresi told the legal group, the American Constitution Society.

“One of the things that is at stake is the assertion by the democracy that when that has happened, it is important to put that person out regardless of policies, regardless of anything else,” the judge said. “That’s got nothing to do with the politics of it. It’s got to do with the structural reassertion of democracy.”

Several legal experts said yesterday that Judge Calabresi crossed an ethical line by advocating President Bush’s defeat at the polls.

“It would I think be violating the ethics rules,” said a law professor at George Mason University, Ronald Rotunda. “I can’t imagine there’d be an ethics professor in the country that would advise Calabresi to do this.”

“It’s a free country, but I think federal judges are supposed to be divorced from the political process,” Mr. Rotunda said. He said the comments raised doubts about whether the judge could be fair in politically sensitive cases.

The issue was hotly debated yesterday on several law-related Internet blogs, including a popular one maintained by a professor at the University of California-Los Angeles law school, Eugene Volokh. Mr. Volokh pointed to a federal judicial canon that says, “A judge should not… make speeches for a political organization or candidate or publicly endorse or oppose a candidate for public office.”

Mr. Volokh said enforcing the rule might violate the First Amendment, but judges should still conform to the canon for ethical reasons. “It seems that the comments at the American Constitution Society meeting transgressed that constraint,” he wrote.

Judge Calabresi declined to be interviewed for this story.

“It’s not appropriate for him to talk to any reporters at this time,” an official at the court’s offices in Manhattan said.

An expert on legal ethics at New York University, Stephen Gillers, said he views Judge Calabresi’s statements as a legitimate exposition of political theory.

“I believe that in his mind, he was not speaking politics. He was not hiding his distaste for the president, which everybody knows, but he was making a point about political legitimacy, political authenticity, and democratic theory,” Mr. Gillers said.

Mr. Gillers said the judge was entitled to some latitude because he was speaking at a legal conference and not to the general public. “He was being slightly hyperbolic as a way of attracting attention to the fine intellectual point he wanted to make,” he said.

Mr. Volokh said Judge Calabresi’s analogy to Hitler and Mussolini was factually inaccurate and unfair, but not a breach of ethics. “There is no canon about comparing Bush to Hitler,” the professor said.