Robert Mueller denounced President Donald Trump’s decision to commute the sentence of his longtime ally Roger Stone in an op-ed published Saturday in The Washington Post. Titled “Roger Stone Remains a Convicted Felon, and Rightly So,” the essay lays into Trump’s reasoning for freeing Stone, who was found guilty of lying to Congress, obstructing a congressional investigation, and witness tampering and sentenced to 40 months in prison. Trump has long maintained that Stone was the victim of overzealous prosecutors and a special counsel whose investigation was nothing more than a hoax aimed at denigrating Trump himself. The former special counsel responded, “The Russia investigation was of paramount importance. Stone was prosecuted and convicted because he committed federal crimes. He remains a convicted felon, and rightly so. Russia’s actions were a threat to America’s democracy. It was critical that they be investigated and understood.” Earlier in the day, the commander-in-chief shared a tweet claiming Stone was “framed by Mueller.”