Cheap shot, I know.

I'd say it happened in baby steps; slowly and methodically taking each next step while lulling the public to sleep. Poor education and retoric ensures that the public does not think critically about it's government. Privatization of government systems and corporate interests insure that maximizing profits outweighs public interest (encarceration pays better than rehabilitation).

The government's petition website seems a complete farce. "legalize pot" was in the first three petitions and when it hit the minimum signatures the goverment coughed out a boiler plate response regurgitating policy based evidence rather than allowing any discussion of fact based evidence. And of course once a petition is responded to, it's frozen from collecting any more signatures so that pesky surfs can't continue to be represented. (I did not that the petition the day after was "actually take these petitions seriously and allow open discusson")

It's not all the US though, the UK gov is completely beyond any rational discussion of the drug issue to the point that there own lead scientific expert was pushed out for not following the political agenda (he's now presented research that an affective anti-depresent could be derived from magic mushrooms but the gov won't allow further reasearch because the medication is derived from a "bad" natural source instead of a pharmacutical company lab). And our gov here came very close to rational thought until your gov pushed them to drop all discussion of even decriminalizing pot. Highly adictive substances like alcahol and tobacco are "ok" but less harmful and less addictive substances remain under prohibition.. hm...

It's a mess all around really. Everywhere got an elite minority spending most of it's time worrying that someone is enjoying there life differently than the puritans and governments would like.