You can demand anything that you want. Doesn't mean you will get it.
Customs and Border Control Police do not need a warrant to search your car if you are within 100 miles of an international border or port (or airport). The laws under which they are chartered give them that authority. There are repeated official rulings which confirm this.
Folks in the FBI are green with envy.
Unconstitutional, you say? Violates the 4th Amendment, you say? Raise several million dollars for lawyers, and get a number of Congressmen supporting you, and maybe a court challenge could prevail. Lacking this kind of backup, you had best do what the nice Policeman says, or plan for a stay in jail.
We have come a long way, and not in a good direction.
They don’t need a warrant to look in the open passenger compartment of your car. If they want to pull it apart or open the trunk they need probable cause.