Wait, last 40 years? What makes that your metric? Marijuana was outlawed in 1937, heroin in 1925. And the Black Panthers were in part a reaction against hamfisted selective enforcement of dumb laws - including drug laws - by the powers-that-be.
IIRC the sort of zealous enforcement of drug laws we see now, didn't really gain traction until the 60s and 70s, which supports slurry's argument.
You don't think drug laws were zealously enforced during Prohibition in the 1920s? Or during the 1950s? I'm just not seeing it. There have been moral panics over drugs leading to ludicrous overreach (at various levels of government) on quite a regular basis since well before "Reefer Madness". It didn't start with "crack babies" and "glue sniffing" - claims that the latest new drug (whatever it is) is different and more addictive and more dangerous than any prior drugs and this makes users extra dangerous to deal with which justifies using extra force or even shooting people with higher caliber weaponry, goes back at least a century.
No, I don't, not to the extent they are now. We didn't send people to jail for life for simple possession of anything, and we didn't have a fucking "Drug Czar" either.
Drug prohibition is old. But the militarized quasi-Schmittian state organs devoted to enforcement them, and their attendant juridical pretexts, are of a more recent vintage.