Pelosi is in charge of the House Chamber and she could simply keep it closed that evening, with lights out and doors locked
Well good. Trump should make this a big deal of this. He should put Pelosi uncontrovertibly on the record stating that Trump is prohibited from entering the House. He should demand a written statement from her. We don’t want any wiggle room from the Dems re-writing of history (as is often done by the left) stating somehow that Trump didn’t want to give the speech at the House.
He should call this censorship of the first order, make this a big issue and include this in his SOTU.
That appears to be her prerogative, and that may be entirely reasonable - consider how distasteful it was when Obama visited the Supreme Court and remained leaning in an Alpha Dog commandeering and disrespectful manner on the CJ's chair.
Trump may not demand the House chamber be made available but McConnell might formally request a Joint Session which will refer to the existence of adequate security.
Pelosi will almost certainly disagree and Trump can then refer to the deep fracture that presently exists in our government - all based on the Dems desire for weakened U.S. border security.
A desire bolstered by the denial of certain government employee paychecks until Trump capitulates