The U.S. Supreme Court on Monday announced it has adopted a code of ethics. It’s about time: Lower federal judges are bound by written codes to help ensure they aren’t using their jobs to advance their personal interests.

Of course, any rule is open to interpretation. Does accepting lavish gifts and vacations from a conservative political donor constitute “the appearance of impropriety” (Clarence Thomas)? What about selling books at college appearances (Sonia Sotomayor)?

How the rules will be enforced remains an open question. Let’s hope the justices can live up to the spirit, as well as the letter, of the code.