This is backwards. First you need philosophical clarity regarding national borders, then you can apply that knowledge to practical problems related to the war on drugs or the welfare state.
I agree in principle, and, look, we didn't even have to solve the drug war first. Though we might disagree on what qualifies as "a very real threat to individual rights." For example, you don't mention anti-individual rights ideologies, like socialism. Binswanger has argued against controlling for political ideology at the border. I disagree and have debated the point at length on the "Immigration Restrictions" thread.