In foreign affairs, American presidents have a free hand.  The Constitution is short and sweet on the subject.  "The President shall be Commander in Chief" is all it really says.  Congress has to declare war, but it has declined to effectively exercise this power, deferring to the president.  The courts are extremely deferential to the president in foreign affairs.  Divided counsels are dangerous, and this country has but one voice when it speaks to the world: that of the President.

Right now, our president is beyond ticked off.  He and his country are being disrespected by the Mexican government.  The Mexicans in charge are turning a blind eye to the invasion from Central America — while they laugh at us from behind our backs.

Trump won't put up with it.  He can't.  His credibility is on the line.  If the Mexicans can make a fool of him, he loses respect, everywhere.  A president cannot allow that to happen.

He won't shut the border, but don't underestimate the power of an American president to have his way in a dispute with a foreign country.  We have Mexico by the throat economically, and there are many ways to start squeezing.

Then again, maybe I'm wrong about Trump.  Maybe he's all talk.

Fritz Pettyjohn has practiced law for 45 years.  He blogs at ReaganProject.com.