As far as I know, every state in the union allows the use of deadly force to defend oneself from assault. Where do you not have the right to shoot junkies (or, for that matter, perfectly sober people) dead on the spot if they assault you or yours?
But my greater point is this: most of the so-called libertarian anti-drug war advocates you see have nothing to say on the responsibility side of the equation.
If the consequence of indiscriminate drug use was unemployment without legal recourse, cirrhosis of the liver without government medicaid, dying in an alley without anyone stopping to look, mandatory attempted murder charges against anyone driving a vehicle with ANY intoxicant in their system, etc., then I might have more sympathy to their cause. But as long as society has to carry the burden of the dregs of druggies, it also has the right to try to abate the problem in any way the society collectively decides.