They want Mexican trucks to roll freely through the U.S. without any U.S. laws getting in the way. The U.S. and its laws will be subordinated to the SPP/NAU "agreement".
Mexican trucks will have some form of rolling diplomatic immunity. Cool. Now I can buy Bohemia by the truckload in Vera Cruz cheap, and have it delivered without the revenoors getting in the way.
Now, if I could figure out a way to truck beer from Munich.