He offered to dispatch NG, but that request legally had to come from the Capitol Police (which does not report to the Administration branch in any way), just like NG can't be deployed in states without the governor specifically requesting same and declaring a formal State of Emergency.
From Wikipedia:
"Before invoking the powers under the Act, 10 U.S.C. § 254 requires the President to first publish a proclamation ordering the insurgents to disperse."
It hasn't been invoked without state/local request since Kennedy.
"Not just a good idea... It's the law."