US President Donald Trump speaks while signing executive orders at the White House in Washington January 24, 2017. [Photo/Agencies]

As president, Trump can use an executive order to halt refugee processing. President George W. Bush used that same power in the immediate aftermath of the Sept. 11 terrorist attacks. Refugee security vetting was reviewed and the process was restarted several months later.

Other executive actions expected Wednesday include bolstering border patrol agents and ending what Republicans have argued is a catch-and-release system at the border. Currently, some immigrants caught crossing the border illegally are given notices to report back to immigration officials at a later date.

If Trump's actions would result in those caught being immediately jailed, the administration would have to grapple with how to pay for jail space to detain everyone and what to do with children caught crossing the border with their parents.