A commission of the American Bar Association has recommended that the group weaken its code of judicial conduct by changing, from a mandatory rule to nonbinding advice, an instruction to judges to "avoid impropriety and the appearance of impropriety."

Supporters of the change say disciplining judges for violating a concept as vague as "the appearance of impropriety" is unfair. Opponents denounce any retreat from the longstanding and widely embraced standard, and one critic � Robert H. Tembeckjian, the administrator of the New York State Commission on Judicial Conduct � has resigned in protest as an adviser to the A.B.A. commission.

"At a time when the A.B.A. is defending judicial independence from relentless attack," Mr. Tembeckjian wrote in a resignation letter on Saturday, "I cannot imagine that either the judiciary or the public will applaud the A.B.A. for relegating the �impropriety and appearance of impropriety' standard to a virtually meaningless phrase."

The change is part of what would be the first comprehensive revisions to the association's Model Code of Judicial Conduct since 1990; the revisions now go before the group's House of Delegates, which meets in Miami next week, before they can become formal policy. Individual states often look to the model code as a template for their own judicial ethics codes, violation of which can lead to punishment as severe as removal from the bench.

The change was a late-breaking development, coming more than three years after the commission began a periodic review of the code.

The very first canon of the proposed revisions continues to say that judges "shall avoid impropriety and the appearance of impropriety."

But recently added language in the introduction to the code says that while that and other canons provide "important guidance," judges cannot be disciplined for violating them. The canons are followed by rules that are more specific (judges may not, for instance, use the prestige of their offices for financial advantage), and the new introduction says that only those rules may serve as the basis for discipline.

Cynthia Gray, the director of the Center for Judicial Ethics of the American Judicature Society, a nonpartisan group promoting judicial independence and integrity, questioned the commission's strategy.

"To leave it in the language and later say the language doesn't count," Ms. Gray said, "is strange and inexplicable to us."

Mark I. Harrison, the chairman of the A.B.A. commission, said the "appearance of impropriety" standard was vague and added nothing to the rules prohibiting specific conduct that remain mandatory.

"We think it's a step forward," Mr. Harrison said of the commission's decision. "It is important as a matter of due process and fairness to make clear what would be the basis for disciplinary enforcement without ambiguity and without confusion."

Jonathan Lippman, New York's chief administrative judge, disagreed, saying the "appearance of impropriety" standard was sensible and workable. "I don't think this is nuclear science," he said. "Judges overwhelmingly approve of that standard as a basis on which to go about their daily business."

The association has urged judges since 1924 to avoid the appearance of impropriety, and returned to the subject in 1972 and 1990.

"Every time the A.B.A. addressed this standard, it was strengthened," Mr. Tembeckjian wrote in his resignation letter. "Until now."

Victoria Henley, the president of the Association of Judicial Disciplinary Counsel, whose members hear and consider complaints against judges, said the recent revisions were unlikely to gain wide acceptance. "If they basically gut the �appearance of impropriety' standard," Ms. Henley said, "it's unlikely that the A.B.A. will continue to be responsible for drafting a model code that will be used by any state."