By tradition, the president (executive) is invited annually by the House of Representatives to address a joint session of Congress on the State of the Union. This is not mandated by law, except for the general expectation that the president will keep the congress informed. Also by tradition, the event is held in the House chambers because its size can accommodate both the House and the Senate members. Thus, the invitation goes to the president from the Speaker of the House of Representatives (currently Nancy Pelosi), although resolutions to back the invitation are traditionally passed by both the House and the Senate.
At this point, those resolutions have not been passed, although the initial invitation to President Trump had been sent and the date set for January 29th.
A gathering in one place of the president, the vice president, all but one cabinet member, all members of the House, Senate, the Supreme Court, as well as the top military commanders -- is an extraordinary collection of our government in one place and one time. The unlikely, but devastating, risk of an almost complete eradication of our governing bodies requires the utmost in logistical planning and manpower security.
Only the one "designated survivor" -- usually a lower level cabinet member -- is chosen not to attend so there would be one member of the government surviving a catastrophic disaster and able to preserve the continuity of government.
All that is background to Speaker Pelosi's decision to postpone the State of the Union gathering on January 29th, given that the government is shut down. Whether out of genuine security concerns, given that security officers are working without pay, or whether this is a cover for not wanting to give President Trump the bully pulpit to bray out his side of the shutdown controversy -- Speaker Pelosi has written to President Trump asking they find another time to schedule the even after the shutdown has ended.
She has also suggested as an alternative that he could give the speech in writing. Or he could give it by television from the Oval Office.
Whatever the official reasoning, there's no doubt that there is a power play going on here. Pelosi is sending Trump a message that she too has power. The Constitution gives her as Speaker the right to invite -- or not -- the president to give the speech.
So score another win for Nancy Pelosi -- and, incidentally, score another one for exerting the power of Congress -- and another for a woman standing up to a man.
Ralph