Ditto the 2nd. If a needle is just another weapon designed to pierce people like a knife or bullet, and anyone brandishing random mystery substances at you is issuing a death threat by performing this aggression, then laws already exist concerning options on the table that citizens can use in defense of their lives and property.

The worlds population had a ringside seat to the killing and maiming of hundreds of millions of people using needles. Its no longer an obscure weaponized killing platform, but a very public one.