In an Aug. 4 2018 appearance on Fox News, Penn called Mueller's investigation into Russian collusion “a national waste of time". Penn published several columns which criticized Special Counsel Robert Mueller and political and legal adversaries of Trump. In online opinion columns, he alleged that Mueller and "Democratic-leaning lawyers" were acting improperly in trying to prepare a charge of obstruction of justice against Trump. In these articles, Penn did not disclose that his firm had previously done work for Trump in the 1980s.