Updated at 2:35 p.m. on February 22.

On its face, the charge that Justice Clarence Thomas or any other member of the Supreme Court has violated ethics rules is a hard one to swallow. Recent allegations of bias and conflict of interest have been vigorously rejected—not just by his conservative allies, but also by well-respected progressives.

“We see no basis for the accusations that the Justices’ decisions are based on anything but the merits,” said Michael Waldman, executive director of the Brennan Center for Justice at New York University’s School of Law, in a strongly worded statement. “And people should think very hard before asking prosecutors to investigate judges just because they dislike the decisions they make.”

Waldman’s reluctance to jump on the anti-Thomas bandwagon is understandable. Legal scholars warn that too much congressional meddling could compromise the independence of the judiciary. Short of impeachment, in fact, the Constitution gives Congress precious little leeway to regulate the nation’s highest court.

But a string of recent controversies over alleged ethics conflicts and violations by Thomas and other justices points up what some argue is a gaping hole in Supreme Court ethics rules. In theory, the Supreme Court embraces the code of conduct set by the Judicial Conference, which administers the U.S. courts. But compliance by the high court is strictly voluntary, and recusal decisions are left solely up to individual justices.

“I think the time has come for them to be treated like other judges and other public officials,” said Amanda Frost, a law professor at American University. Frost acknowledged that there’s no reason to believe that any sitting Supreme Court justice has crossed ethical lines. But the absence of transparency and oversight invariably raises questions, she said. “The problem is that we don’t really know what’s going on, so there’s a lot of speculation and discussion,” said Frost.

Some on Capitol Hill agree. What started as a one-day story instigated by liberal activists at Common Cause has mushroomed to include calls for legislation and for Thomas to recuse himself from constitutional challenges to the new health care law. At issue is whether anti-health-care activism by Thomas’s wife, Virginia, presents a conflict.

“In such a highly politicized case, it’s important that the American people feel this process is on the level,” said Rep. Anthony Weiner, D-N.Y., who has gotten some 90 of his colleagues to sign a letter calling on Thomas to recuse himself from any health care deliberations. Weiner has even set up a website inviting citizens to cosign his letter.

Another House Democrat, Rep. Christopher Murphy of Connecticut, is drafting legislation that would apply the Judicial Conference’s code of conduct to the Supreme Court and, among other changes, require justices to publicly explain their reasoning when they recuse themselves from cases.

“Congress shouldn’t judge any one justice or any one conflict-of-interest claim,” acknowledged Murphy. “But Congress does have a legitimate role in setting up the rules of the judiciary so parties have a level of assurance that they’ll get a fair shake.”

Some on Capitol Hill have long argued for stronger judicial oversight. For several congresses in a row, Sen. Chuck Grassley, R-Iowa, and Rep. James Sensenbrenner, R-Wis., have teamed up to craft bills that would create an inspector general for the judicial branch. The lawmakers reintroduced their bills this month. A key difference between their bills is that Sensenbrenner’s would apply only to the federal and appellate courts, but Grassley’s would give the inspector general oversight over the Supreme Court as well.

Legislation also may be in the offing from Senate Judiciary Chairman Patrick Leahy, D-Vt., who last year introduced a bill that would allow retired Supreme Court justices to sit on the high court when an active Justice recuses himself.

Common Cause and the Alliance for Justice also are calling for congressional hearings. Common Cause last month called on the Justice Department to investigate whether Thomas and Justice Antonin Scalia should have recused themselves from the Citizens United v. Federal Election Commission ruling, because the two allegedly attended retreats sponsored by David and Charles Koch, billionaires who benefited from the ruling. Common Cause also has questioned errors on Thomas’s financial disclosures, which he has since corrected, and about whether he failed to report a Koch-funded trip.

It’s not the first time a justice has been accused of an ethical breach. The Judicial Conference’s code of conduct states that judges should “refrain from political activity,” and from personally participating in fundraising activities. Yet Justice Samuel Alito, for one, has reportedly spoken at and attended fundraisers for conservative groups. Some congressional Republicans contend that as the Obama administration’s former solicitor general, Justice Elena Kagan should recuse herself from health care deliberations.

For the moment, at least, the Supreme Court enjoys much higher approval ratings than either the White House or Congress. But public opinion could change if justices become increasingly politically active, say legal ethicists, and Congress may face pressure to step in.

“It’s our belief that the Supreme Court justices should be subject to the same ethical code of conduct and standard that other judges abide by,” said Nan Aron, president of the Alliance for Justice. “At the moment, they can do pretty much whatever they want.”

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