Don McGahn didn’t send his regrets to Jerrold Nadler. The White House took care of the RSVP instead. Donald Trump invoked executive privilege yesterday on conversations with his former White House counsel, setting up a legal fight with the House Judiciary Committee. Or more accurately, another legal fight:

CNN called this “stonewalling” on Trump’s part, but the Washington Post took a more neutral tone to the dispute:

The White House on Monday blocked former counsel Donald McGahn from testifying to Congress, the latest act of defiance in the ongoing war between House Democrats and President Trump.

McGahn, who Democrats hoped would become a star witness in their investigation into whether Trump obstructed justice, was subpoenaed to testify Tuesday morning. The former White House counsel delivered critical testimony in several instances of potential obstruction by Trump detailed in special counsel Robert. S. Mueller III’s report.

The Department of Justice issued a new legal opinion yesterday that stakes out significant ground on executive privilege. Assistant Attorney General Steve Engel wrote that Congress has no business subpoenaing White House officials who have no connection to legislative authority, in comparison with those working in Cabinet agencies and federal bureaucracies, which share legislative and executive powers from both branches. That immunity applies to all conversations, not just those specific to a topic of interest for Congress, Engel claims, an astonishingly broad claim that would squelch almost any kind of subpoena to White House personnel no matter the circumstances.

That argument might get clipped by the courts, but another argument sounds stronger in terms of executive privilege. Congress has argued that Trump’s waiver of privilege with McGahn and others for Robert Mueller’s investigation was permanent and plenary. Engel argues in his brief that Trump can issue limited waivers that only apply within the executive branch that the legislative branch cannot then use against him. Mueller was working within the DoJ as special counsel rather than a fully independent prosecutor, as he would have been under a previous law. Given that executive privilege is specifically a shield from legislative intrusion, that argument seems likely to score some points in federal court, even if Engel’s blanket-immunity argument doesn’t carry the day.

Technically, McGahn doesn’t have to comply with the White House bar on his testimony. However, McGahn’s current law firm announced that he would “respect the President’s instruction”:

In a letter to the committee obtained by The Washington Post, McGahn’s lawyer, William A. Burck, said the former counsel would not testify.

“Mr. McGahn remains obligated to maintain the status quo and will respect the President’s instruction,” Burck wrote.

Testifying could jeopardize business and professional standing for McGahn, who works for Jones Day, a Republican law firm with close ties to the Trump campaign and electoral politics. Jones Day will still be involved in the reelection campaign but will have a reduced role from 2016, campaign officials say, when they were the main firm.

Unfortunately for McGahn, Nadler will have to come after him directly to challenge the executive privilege claim. Jones Day is going to be busy on McGahn’s behalf for quite a while.

This will all end up in court, but it’s entirely theater anyway. Congress already has Don McGahn’s Greatest Hits from the Mueller report. Mueller wasn’t likely to hide worse incidents than those included in Volume II, so the only thing McGahn would be supplying is additional context — and that might not be so helpful to House Democrats looking to impeach Trump on obstruction charges. Nadler knew this wasn’t going anywhere, and so he’s taking the tactic that will produce maximum outrage while adding minimum substance.