Ever since I converted libertarian, I've been against the War on Drugs. It's a violator of personal liberties and is ineffective in preventing drug use. Most people who are arrested for drug use didn't cause harm towards other people. When I hear pro-drug war arguments, I'm reminded of arguments government welfare on the left (take the war on poverty). The drug war makes criminals out of people who otherwise wouldn't be and the war on poverty keeps or puts people into poverty who otherwise wouldn't be.
But not only is the drug war ineffective in preventing what it intends to prevent, it grows the power and scope of the federal government. It feeds power into the police state and the military industrial complex. It violates the 10th amendment and the principle of federalism. Though this is starting to change with states legalizing marijuana whether it's medical or recreational. As many as 13 states could see marijuana ballot proposals this year (particularly CA, AK, AZ and OR).
There's a couple of great YouTube vids I wanna post. One is from Tom Woods talking about the Police State and the other is of Stefan Molyneux on ending the drug war. Highly recommend you check both out and let me know what you think.