The legal authority to use force is against the drug cartels and they use the legal border crossings and trucks to bring their goods to market. They use shorelines and half subs as well.
The ONLY proven method of ending illegal border crossings is to work with the countries of the northern triad to stabilize governments, stop drug trafficking, and establish an economy where people work a job to provide a living for families. These countries are also stressed by the collapsing climate of Earth.
So, the Republicans in Congress are nothing more than cowardly Paper Tigers.