NEW YORK — In a sharp rebuke of President Donald Trump, a Manhattan federal court judge ruled Tuesday that the Department of Justice cannot intervene on Trump’s behalf in a defamation lawsuit brought by a magazine columnist who accused him of sexual assault in a department store in the 1990s.The ruling by Judge Lewis Kaplan means E. Jean Carroll’s lawsuit against Trump — in his personal capacity as an ordinary citizen — can proceed. If Kaplan had allowed the Justice Department to represent Trump, the case would have likely been dismissed because the federal government cannot be sued for defama…