The acting head of the Drug Enforcement Administration is planning to leave his post later this month after losing confidence in President Donald Trump’s respect for the law, a source familiar with the decision said Tuesday.

Chuck Rosenberg, a longtime federal prosecutor who was named to oversee the DEA in May 2015, previously served as chief of staff to James Comey, the FBI director fired by Trump in May.

Rosenberg’s concerns about Trump went public early last month, after the DEA chief sent an unusual agency-wide memo that essentially rebuked the president. The email followed a suggestion by Trump at a law enforcement-focused speech on Long Island that police were being “too nice” to suspects and might not want to shield their heads from hitting the roof of the police car during arrests.