The collective significance of the Supreme Court’s opinion in the Nixon case and Chief Justice Marshall’s conclusions in the Burr trial is that in a criminal case, constitutional imperatives might require a president to submit to compulsory judicial process. A defendant in a criminal case has a constitutional right to confront the evidence against him and must be able to command production of that evidence, even if it is in the hands of the president.

On the other hand, a prosecutor also has a strong claim to evidence essential to the enforcement of criminal statutes. While the president’s presumptive privilege against compulsive testimony would be entitled to considerable deference, that claim could be overcome if the prosecutor makes a strong showing that he must have specific essential evidence that is not procurable from other sources and that he is not simply engaged in a fishing expedition.

As things currently stand, Mueller has made no application to a court for a subpoena to the president based on showing a need for specific evidence essential to his prosecution and not available from other sources. News sources have published a long list of subjects said to be of interest to the special counsel, but these subjects, if they are, indeed, coming from Mueller’s office, are in many cases vague, open-ended and highly generalized—all the earmarks of casting a very wide net to see what might be snared. He’s going to have to do better than that—the usual open-ended general subpoenas won’t work.