A group of more than a hundred law professors from across the country has asked Congress to extend an ethical code of conduct to the Supreme Court - for the first time - and clarify when individual justices should step away from specific legal cases.

The group's appeal on Wednesday, in a letter to the House and Senate Judiciary committees, comes after recent controversies involving travel and appearances at political events by several Supreme Court justices, including Clarence Thomas and Antonin Scalia. Rep. Christopher S. Murphy (D-Conn.) said he plans to introduce legislation that addresses the issue.

Thomas and Scalia have been criticized by a public interest group for attending private political meetings sponsored in January 2007 and 2008 by David and Charles Koch, conservative billionaires who made large contributions during last year's election and have financially backed the tea party movement.

Precisely what happened at those meetings remains unclear, but neither of the justices' routine financial disclosures mentioned that the Kochs had organized the events. Supporters of reform say that would change if the same ethics rules that applied to lesser judges were applied to the Supreme Court.

The Kochs own oil, gas and paper businesses involved in hundreds of legal cases in federal court. The nonprofit group Common Cause has complained that the controversial Citizens United v. Federal Election Commission decision on campaign financing last year - on a narrow majority backed by Thomas and Scalia - opened the door to heightened corporate contributions from the Koch empire.

Hurdles ahead

Justice Samuel A. Alito Jr. also has provoked criticism from liberal groups for attending or speaking at two annual fundraising dinners sponsored by a politically oriented magazine, the American Spectator. The ethics code for lower courts states that judges should not participate in fundraising activities or "use or permit the use of the prestige of judicial office for that purpose." Alito was quoted by a reporter at one of the events saying his attendance was not important.

The group's appeal for legislation faces political as well as potential constitutional hurdles, partly because members of the Supreme Court are now the final authority on the appropriateness of their ethical behavior. Decisions to recuse, or step away from deliberations, by tradition have been left up to the individual justices at the center of any complaint, contrary to the practice on most state supreme courts.

The professors said in their letter to the committees that their goal is not to second-guess the activities of any individual judge but to create "mandatory and enforceable rules to protect the integrity of the Supreme Court." An influential British judge declared in the 17th century that "no man may be a judge in his own case," the letter said, but "inexplicably we still allow Supreme Court justices to be the sole judge of themselves on recusal issues."

Under the ethics code that the lawyers consider their model, approved and regularly updated by the nation's chief appellate judges under the chairmanship of the chief justice, lesser judges are prohibited from accepting travel reimbursements from outside groups if they "give the appearance of influencing the judge" or "otherwise give the appearance of impropriety."

Nan Aron, director of the liberal group Alliance for Justice, said that if these rules were extended to the Supreme Court, none of the justices could attend "overtly political meetings or events" like those sponsored by the Kochs.

According to their financial disclosures, Scalia and Thomas were each reimbursed for travel to the Koch seminars by the Federalist Society, which had no meetings of its own at the venue, an exclusive resort in Indian Wells, Calif. "We knew the justices were going to be out there," and the attendees would be interested in hearing what they had to say, said Eugene Meyer, the society's executive director.

The Federalist Society, according to its public tax returns, has received at least $1.4 million from the Kochs during the past decade through their family-run charitable foundations, including $75,000 each year to cover expenses in 2007 and 2008 - the years that Thomas and Scalia were reimbursed.

The society also paid for the travel expenses of Thomas's wife, Virginia, according to Kathy Arberg, a Supreme Court spokeswoman. She said Thomas spoke about his autobiography at a dinner and dropped by only one of the Koch-organized seminars but cannot recall what was discussed. She said that two of the four days listed by Thomas as being reimbursed in California were spent in travel but declined to detail how he spent the rest of his there.

Looking for standards

Although other jurists must report their attendance at all privately sponsored educational seminars, "the question of whether a particular event is to educate judges . . . is not applicable to the Supreme Court," Arberg said.

Rich Fink, executive vice president of Koch Industries, called any allegations that the firm was trying to influence Thomas and Scalia flimsy and hypocritical.

Asked why Thomas's reimbursement for a single speech stretched to four days, Meyer said, "If you pay for someone to go out, you don't care when they come back." He promised to look into the matter but did not return a series of phone calls. He also did not respond to a question about whether the society's revenue from the Koch family was directly spent on the justices' travel to the seminars.

At present, said Ellen Yaroshefsky, director of the Jacob Burns Ethics Center at the Benjamin Cardozo School of Law, "we have standard-less standards" at the court that she struggles to explain to students.

She said it would be straightforward for the court to appoint an independent body of retired justices or other experts to adjudicate recusal and ethics controversies.

The court issued its last joint statement on recusal policies in 1993, when it set out some general ground rules for recusals involving justices' families but cautioned that "even one unnecessary recusal impairs the functioning of the court."