While it’s true that CBP has immigration authority well inside the border they have zero authority to operate without approval of the local sheriff. And they have even zeroer authority to go wading around private or state property without appropriate warrants. And if there is wire or other security measures on private or state land, supreme court be dammed, they had best mind their manners before screwing with it. They really, really, need to keep their wire cutters in their pockets.
Not true when after illegals. Most sheriffs withing 100 miles are in coalition partnerships with the feds and cooperate on aliens and drug trafficking. See HIDTAs. In all 50 states.