(CNN) Don McGahn's name hasn't been in the news much of late. But a judge's ruling Monday that the former Trump White House general counsel cannot resist a subpoena to testify from Congress in its ongoing impeachment hearings has wide-ranging implications for a number of senior administration officials tied to the Ukraine probe.

"However busy or essential a presidential aide might be, and whatever their proximity to sensitive domestic and national-security projects, the President does not have the power to excuse him or her from taking an action that the law requires," Judge Ketanji Brown Jackson wrote in her opinion, adding: "Stated simply, the primary takeaway from the past 250 years of recorded American history is that Presidents are not kings."

That ruling is in the process of being appealed and could well end up before the Supreme Court. But in affirming the findings of lower courts, what Jackson did is send a clear signal that executive privilege cannot be claimed overly broadly to keep aides and former aides to speak about potential wrongdoing that they either witnessed or were a part of.

It's in keeping with the argument put forward over the weekend by House Intelligence Committee Chairman Adam Schiff (California) regarding decisions by McGahn as well as acting White House chief of staff Mick Mulvaney and Trump personal attorney Rudy Giuliani to resist House subpoenas to testify on Ukraine.

"Because we have adduced so much evidence of guilt of this President, so much evidence of serious misconduct, any privilege the President would have would be vitiated by this crime-fraud exception," Schiff told CNN's Jake Tapper

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