That's an easy one. Trump was the sitting President on J6 and the President is the only one able to declare the Insurrection Act. So he would have had to declared it on himself.
But... President Trump did follow proper protocol and first asked (proclamation) "them" to disperse and go home written in a Tweet on Twatter that was later strangely removed from public eyes.
So who was "them" is the entire key to the story.
Who gave the order to unlock the magnetic doors?
Why haven't they released the other video (front) on the suspected pipe bomber?