Why aren’t all the president’s men testifying?

Some of the president’s closest aides, official and unofficial, past and present — Robert Blair, Michael Duffey, Rudy Giuliani, Don McGahn, Mick Mulvaney and Mike Pompeo — invoke a presidential order to refuse to give evidence about delays in Ukraine aid. But government officials like Gordon Sondland, William Taylor, Alexander Vindman and Marie Yovanovitch all ignored such orders and gave valuable testimony. After weeks of tweeting, giving interviews and writing his memoirs, John Bolton has let it be known that he will testify before the Senate, if he is subpoenaed by the Senate. But what gives him the right to dictate terms?

Mr. Bolton’s statement Monday claims that he is trying to “resolve the serious competing issues” between his obligations as a citizen and a former national security official. In fact, those obligations point in the same direction. Like jury duty or paying taxes, testifying under oath about facts we know is not optional; it is a fundamental obligation of citizenship. As a government official, Mr. Bolton held high office under an oath to “support and defend the Constitution.” Testifying at a Senate impeachment trial fulfills that constitutional oath.

Anyone who served in high public office knows that testifying before Congress about matters you worked on in government is part of your solemn public duty. If legislators’ questions impinge upon legitimate concerns about executive or national security privilege, you still must appear, declining to answer only those questions that call for information legally protected from public disclosure.

It does not matter that these witnesses have successfully withheld their testimony until now. The House’s impeachment vote should overrule any ethical or legal objection these witnesses now have to testifying before the Senate. How can senators vote on Mr. Trump’s removal without the testimony of any of his closest advisers? And if Mr. Bolton ends up testifying, don’t the Senate and the public need the others’ testimony to flesh out the full story?