cupperman who served as donald trump's deputy national security adviser. house democrats had subpoenaed charles cupperman to testify before the impeachment committees on monday. but in an effort to stop cupperman from doing so, the white house said on friday that the president had invoked constitutional immunity, leaving cupperman uncertain about what to do. quote, plaintiff obviously cannot satisfy the competing demands of both the legislative and executive branches and he is aware of no controlling judicial authority definitely establishing which branch's command should prevail, the suit said. joining us now by phone is a reporter who broke that story, michael schmidt, washington correspondent for "the new york times." might be able, explain exactly what this is. >> well, this is a late friday filing. it's a lawsuit that chuck cooper, the lawyer for cupperman, and the lawyer for john bolton has filed in federal