Deploy military with rules of engagement as applicable in Korean DMZ. Our border guards serve in a war zone under war zone conditions. Allow them to use lethal force when necessary. Untie their other hand Mr. President.
All you need do is embed a BP agent with each platoon on patrol. Same as when the Navy does drug interdiction ops at sea. The US Navy cannot legally board foreign ships but a US Coast Guard officer can. So they assign one to the US Navy ship on patrol. Problem solved.