The following editorial first appeared in the Los Angeles Times:

Two liberal groups have asked the Judicial Conference of the United States to investigate whether Supreme Court Justice Clarence Thomas has violated the federal Ethics in Government Act. The prospect of such an investigation is remote, but the conduct cited by Common Cause and the Alliance for Justice is troubling.

The groups have asked the Judicial Conference to consider two possibilities: that Thomas knowingly withheld information about his wife’s income from financial disclosure forms, and that he misrepresented the amount of free air travel he received from a wealthy friend.

Between 2003 and 2007, Thomas’ wife, Virginia, received $686,589 in compensation from the Heritage Foundation, a conservative think tank in Washington, but the justice wrongly checked the box marked “none” on the question related to spousal income. Thomas says his omission resulted from a misunderstanding of the reporting requirement, and he has since amended his answers. But the situation is peculiar: How could a Supreme Court justice, who must pay attention to the nuances of complicated legal cases, misread instructions on a disclosure form?

Common Cause and the Alliance for Justice want the Judicial Conference to exercise its power to refer a matter to the attorney general when it “has reasonable cause to believe (a judge) has willfully falsified or willfully failed to file information required to be reported.” Establishing that would be difficult, but that doesn’t mean it isn’t worth investigating; full disclosure is mandatory, not optional, and it is extremely important.

In the other matter, the groups want the conference to investigate whether Thomas failed to report that some of his air travel has been paid for by Harlan Crow, a real estate developer who also financed a museum in Pin Point, Ga., Thomas’ birthplace. Thomas’ relationship with Crow is controversial, and questions have been raised about the justice’s role in establishing the museum. But the issue identified by Common Cause and the Alliance for Justice is a narrow one. If Thomas failed to accurately report the source of his travel funds, it would confirm the image of the justice as slovenly when it comes to disclosure requirements.

It’s up to individual justices how closely they want to associate with prominent business and political figures. To our mind, Thomas has been too free in forming such connections. But regardless of his off-the-bench activities, he should follow — and not just make — the law.