The phrase “abuse of power” appears nowhere in the federal criminal code, which lists thousands of criminal laws passed by Congress over the years. But many crimes aren’t written down in codes. Crimes derived from the “common law” — the body of law developed from judicial opinions and legal treatises rather than statutes — have been a staple of American law for centuries. Today in many states, district attorneys routinely charge people with things like “assault,” “forgery” and “indecent exposure” even where no statute makes those things a crime.

Common-law crimes are no harder to define with precision than crimes written down in a statute. Ask any first-year law students for the common law’s definition of burglary and they’ll (hopefully) be able to tell you: “the breaking and entering of the dwelling house of another in the nighttime with the intent to commit a felony.” If someone is accused of burglary in a state where the crime isn’t defined by statute, no defense lawyer would respond by announcing that burglary is vague or made up. Burglary is an established crime, even where its definition exists only in legal treatises and judicial opinions.

President Trump’s defense falls apart for precisely the same reason. As with burglary, American legal treatises and judicial opinions have long recognized the criminal offense of “abuse of power,” sometimes called “misconduct in office.” In 1846, the first edition of the pre-eminent treatise on American criminal law defined this common-law offense as when “a public officer, entrusted with definite powers to be exercised for the benefit of the community, wickedly abuses or fraudulently exceeds them.” The treatise noted that such an officer “is punishable by indictment, though no injurious effects result to any individual from his misconduct.”

Courts from Michigan to Maryland have recently upheld convictions of government officials for committing this common-law crime — despite objections that the crime has never been codified by statute. And the House, in its first article of impeachment, has accused Mr. Trump of exactly what the law prohibits: He “abused the powers of the presidency” for “corrupt purposes in pursuit of a personal political benefit.”

As for “obstruction of Congress,” that’s not only a common-law crime. Versions of the crime have also been listed in the federal criminal code since the 19th century.