The president did not stop the investigation of anyone. He took the Congressional claim seriously and sealed the documents for 45 days, until a court can decide if Congress' claim has any validity. That IS the rule of law. Jefferson's investigation certainly can wait 45 days and it sounds like he is totally nailed already on other evidence.
Wait=stop. Those sealed records can not be viewed by the investigators for at least 45 days. So as it relates to investigating those records the investigation has been stopped.