When it comes to drug abuse, harm reduction can mean providing clean needles and other supplies to the user. The person isn't going to stop just because they're denied clean supplies. In the same way that you can't stop people from acquiring guns, but you can help prevent them from purchasing guns that are fundamentally unsafe to operate.
No, you literally cannot stop people from acquiring guns in the United States, as it's baked in the Constitution. Please make arguments based in reality.
