Bloomberg reports that Justice Breyer heard oral argument on Wednesday in a case involving a subsidiary of Johnson Controls Inc., a company in which Breyer owned shares of stock worth some $33,000. Mrs. Breyer sold the shares on Thursday, after a Bloomberg reporter inquired about the stock ownership.

Let me emphasize that I am confident that Breyer’s participation was an oversight. Further, it would be the rare case when I would have any reason to be concerned that a justice’s stock ownership might influence the justice’s decisionmaking.

That said, it’s a fair question why any Supreme Court justices continue to hold any individual stocks. The Bloomberg article cites “experts in judicial ethics” who say (in the article’s paraphrase) that “the tax implications of a forced sale” weigh against requiring justices to sell off their stock holdings.

But as a result of a 2006 amendment, federal law enables federal judges to defer any capital gains tax that they would otherwise owe on stock sales that are “reasonably necessary to comply with any Federal conflict of interest statute, regulation, rule, judicial canon, or executive order …, or requested by a congressional committee as a condition of confirmation.” Yes, they would first need to go through the procedural step of obtaining a “certificate of divestiture,” but that ought to be a very streamlined process. (Under the statute, certificates of divestiture for judges are issued by the Judicial Conference of the United States “or its designee.” Back in 2006, the Judicial Conference designated the Supreme Court to issue certificates for justices and the Codes of Conduct Committee to issue certificates for lower-court judges.)