An ex-Trump aide wants a judge to decide whether he should testify to impeachment investigators or follow Trump's order not to cooperate

Robert Alexander/Getty Images A former White House adviser is asking a federal court whether he should comply with a subpoena to testify before House impeachment investigators, or obey President Donald Trump's order not to cooperate. Former deputy national security adviser Charles Kupperman filed a lawsuit asking a judge to decide how he should proceed. Theimpeachment inquiry is rooted in a July 25 phone call Trump made to Ukrainian President Volodymyr Zelenskiy, asking him to pursue investigati...