The behavior of Supreme Court justices has come under increasing scrutiny. Questions have been raised, for instance, about the propriety of Justices Antonin Scalia and Clarence Thomas appearing at political strategy conferences hosted by the conservative Koch brothers. Other justices’ activities have also prompted concerns that the line between justice and politics is increasingly blurred.

Regardless of whether one shares fears of politicization, disputes are inevitable so long as the nation’s highest court operates with almost no compulsory ethics rules to guide — or constrain — behavior. The Supreme Court, whose members are shielded with lifetime appointments, is the only entity in our government that is not subject to mandatory ethics requirements. That is why reformers are calling for the Code of Conduct that governs all other federal judges to apply to the justices. Surely it makes no sense to have lesser standards for the highest court than those in place for lower courts.

Some have asserted that Scalia and Thomas are being unfairly singled out by political opponents and that other justices’ appearance at conferences and seminars are being ignored. This charge relies on a false equivalency and a misunderstanding of suggested reforms. Participation by justices in events such as educational seminars, American Bar Association conferences or even meetings sponsored by organizations with strong points of view — such as the Heritage Foundation or the ACLU — is not only permissible but actually encouraged by the code, which allows a judge to speak, write and lecture on the law, especially to law-related groups.

At the same time, the code clearly mandates the avoidance of even the “appearance of impropriety.” It requires judges to “act at all times in a manner that promotes public confidence in the integrity and impartiality of the judiciary.” In Canon 5 it explicitly bans involvement in “political activity” and in Canon 4 prohibits participation in “fund-raising activities” of any kind, political or otherwise. Every federal jurist except Supreme Court justices must abide by these rules.

What sets the Koch brothers’ meeting apart from, say, a speech to the Federalist Society, is that the event was transparently political. The Koches’ own materials have described these gatherings as featuring “plans to activate citizens” and to “change the balance of power in Congress this November,” and bragged that past “participants committed to an unprecedented level of support.” No reasonable person can doubt that this was a meeting with a fundamentally electoral purpose.

The Code of Conduct doesn’t frown on ideological activity but does prohibit political activity, and that’s where Scalia and Thomas crossed the line. The fact that they did so with seeming impunity demonstrates that voluntary adherence to ethical standards doesn’t always work. How to enforce such a code would be the hardest question, but there are options — possibilities include adjudication by other sitting justices, retired justices, lower court judges, the judicial conference or some combination of these. Exact methods could be explored in congressional hearings.

No one questions the right of the justices to give speeches or attend meetings such as those cited in the Feb. 21 Post editorial “The justices’ junkets.” They can even have travel costs reimbursed, as long as there is complete disclosure. So, if the code were applied in this way, could Stephen Breyer continue to attend the World Justice Forum? Is it ethical for Ruth Bader Ginsberg to address the American Sociological Association? Can Justice Thomas speak to law students at a session hosted and funded by the Heritage Foundation? Yes, yes and yes, as long as the meetings were not “political activity” or the justices didn’t “personally participate in fund-raising activities.”

The bottom line is that if the judicial Code of Conduct becomes mandatory the number of events that would be placed off-limits is small. Meanwhile, the effect on the integrity of the court would be large. The Post’s fear that reforms would force justices to “lead cloistered lives” is unfounded.

Some suspect this is an effort by progressives to tweak justices they don’t like. But the Supreme Court itself effectively answered that charge in 2009. In Caperton v. A.T. Massey Coal Co., a case that dealt with a West Virginia Supreme Court justice who ruled in favor of a corporation that had made large contributions to his campaign, the high court said that “codes of conduct serve to maintain the integrity of the judiciary and the rule of law.”

That indisputable principle ought to be applied to the same court that wrote those words.

The writer is president of Alliance for Justice, an association of liberal advocacy organizations.