The President RUNS the FBI. He is constitutionally allowed to tell them what to investigate and what to drop...Period.
The remedy to a corrupt president is through Congress and impeachment.
Not that we actually follow the Constitution anymore.
Bears repeating. It's the bottom line to all this nonsense. The "charge" they are attempting to attach to him is lawful.
Even NBC acknowledged this fact back on Jan 20, 2017:
"Former intelligence officials told NBC News that President Trump would technically have the authority to order an end to the investigation, given that the intelligence agencies report directly to him."
Could President Trump Shut Down An Investigation If He Wanted?