The Speaker of the House has withdrawn her invitation for the president to give the State of the Union address later this month. What if he tries to give one anyway?

President Donald Trump gestures during the State of the Union address in the chamber of the U.S. House of Representatives in Washington, D.C., on January 30th, 2018. (Photo: Win McNamee/AFP/Getty Images)

On Wednesday morning, Speaker of the House Nancy Pelosi sent a letter to President Donald Trump informing the president that he was no longer invited to give his planned State of the Union address to a joint session of Congress on January 29th. Though some headlines reported that Pelosi "asked" Trump to re-schedule his speech, Pelosi's language in her letter, though diplomatic, did not make a request as much as it told the president his options: reschedule, or deliver the address in writing.

"Sadly, given the security concerns and unless government reopens this week, I suggest that we work together to determine another suitable date after government has reopened for this address or for you to consider delivering your State of the Union address in writing to Congress on January 29th," Pelosi wrote.

The State of the Union is presented to a joint session of Congress, so both the House of Representatives and Senate must pass resolutions inviting the president to give the speech. Neither resolution has been passed yet. As speaker, Pelosi can simply refuse to put such a resolution up for a vote, effectively giving her power to enforce her dis-invitation.

With the possibility of a postponed or canceled State of the Union, the nation's media responded with a flurry of histories and explanations. Journalists noted how, until 1913, most State of the Union messages arrived in writing; how President Ronald Reagan's 1986 address was postponed by the space shuttle Challenger's explosion the day before; how presidents William Henry Harrison and James A. Garfield both died before they could give a single State of the Union message.

But one question went unanswered: What if Trump decided to show up anyway? Pelosi may have uninvited him, but what if the president decided to stride into the Capitol building on January 29th, without an invitation?

These days, it's hard to predict what will happen in Washington, D.C. But thanks to the exhaustively detailed notes on rules and procedures maintained by both houses of Congress, we can get an idea of what sort of privileges the president has when he heads to Capitol Hill.

Does the U.S. President Need an Invitation to Enter the Capitol?

The first step for Trump to crash his own canceled State of the Union speech would be entering the Capitol building.

A popular misconception—or, at least, an idea some men have incorrectly declared on Quora—holds that the president can only enter the Capitol building with an express invitation from Congress. The common belief is that the Constitution's "separation of powers" clause, like a restraining order, mandates that an actual physical distance be maintained between the executive and congressional branches of government.

In reality, the president's access to the Capitol has been unrestricted for most of United States history. Indeed, in the country's early days, this was a necessity: Before the 20th Amendment was ratified in 1933, congressional terms and presidential terms both ended and began on March 4th, at noon. Prior to the invention of telephones and fax machines, this forced more than one president to spend the entire night of March 3rd in the Capitol, signing and vetoing a stack of bills passed by the adjourning Congress. (In the 1850s, the President's Room was added to the Senate wing of the Capitol for the president to use on official business. Though various presidents up until Woodrow Wilson regularly used the space, the room—complete with Italian frescos and elaborate chandeliers—today serves primarily for fancy photo ops.)

Trump, like Barack Obama and most presidents before him, has visited the Capitol multiple times, without express invitation, during his own presidency. If he showed up on January 29th, there would be no precedent to restrict his access.

After John F. Kennedy's assassination, however, the security around the president grew so expansive that a president's visit to the Capitol has become a serious logistical affair, requiring significant preparation. Roads need to be blocked off and security sweeps need to be completed.

This security protocol was Pelosi's stated reason for postponing Trump's speech. With the Secret Service and Department of Homeland Security operating on reduced capacity due to the ongoing government shutdown, Pelosi wrote that she was not confident adequate security could be assured for the event.

Can the President Walk Onto the House Floor?

Let's say Trump waves off the security concerns, and arrives at the Capitol anyway. Could he give his speech?

While the president can enter the Capitol building without permission, his ability to stride into the Hall of the House of Representatives—where the State of the Union is traditionally delivered to a joint session of Congress—is a different question.

Entrance to the Hall of the House of Representatives is, in general, restricted only to members performing legislative business. But luckily for Trump, the House rules include a list of other people who are allowed access to the Hall—and the president and vice president are on the list. Other exceptions include Supreme Court justices, governors, foreign ministers, the librarian of Congress, the architect of the Capitol, and "such persons as have, by name, received the thanks of Congress."

The rules of the 116th Congress are yet to be read (for past Congresses, they've been read in late January), but the 115th Congress' rules explained that the Speaker was unable to entertain any motions that would strike down the clause allowing the president to have access to the Hall of the House. This would make Pelosi powerless to stop Trump from entering the floor.

Can the President Give a Speech Without Invitation?

Say Trump walked out into the Hall of the House. Could he clear his throat and start giving a speech?

This is where the president might finally arrive at a road block. The House is governed by a detailed set of parliamentary procedures, which make demands of decorum. There are all sorts of rules determining who can speak when and on what, but, in general, as Speaker of the House, Pelosi controls the flow of debate on the House floor. Without express permission from Pelosi, Trump could not start giving a speech in the Hall of the House.

Of course, parliamentary procedures might not be enough to stop the president from speaking, even if Pelosi bangs her gavel and tells him to stop. This would lead us into uncharted territory. Members who speak out of order open themselves up to "censure or such other punishment as the House may consider proper," according to existing rules. But for a non-member speaking out of order, it's hard to tell what exactly could happen. For protesters interrupting House business, the congressional sergeants at arms and other officers will remove the offending parties. Whether or not this would happen for a sitting president is a question that has not yet been answered in U.S. history.