The gray area here is that it wasn't a subpoena issued by a court. It was issued by Congress. I don't think it is a crime not to comply with a subpoena issued by Congress. HOWEVER, the stuff that was being covered up IS A CRIME. Mishandling of classified information is punishable by law. Since most people in the country never have held a security clearance, they do not know and think this is not that big of a deal.
One thing is clear. There is a very obvious double standard when it comes to hold people accountable. I hope Trey Gowdy succeeds at the end.