(CNN) Since the early days of special counsel Robert Mueller's investigation, President Donald Trump has not only claimed innocence but has argued that the entire investigation is "illegal."

Trump repeated the same argument Friday , tweeting that the investigation "was an illegal & conflicted investigation in search of a crime." In June 2018, Trump claimed "the appointment of the Special Counsel is totally UNCONSTITUTIONAL!"

Facts First: This is wrong -- multiple court rulings have upheld Mueller's appointment, his authority, and the decisions he's made.

A handful of defendants and witnesses ensnarled in the investigation have unsuccessfully tried to invalidate Mueller's authority. Amid this barrage of legal challenges, four trial-level judges and two panels of appeals court judges have ruled in Mueller's favor.

The judges who handed down these decisions were appointed to the federal bench by Democratic and Republican presidents. Here's a breakdown of some of their decisions:

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