One of the selling points of legalization is that states can take a cut of what will be, according to estimates, a $35 billion to $45 billion industry and earmark some of these new tax revenues for good causes. It’s the same tactic used to win public approval of lotteries — and with the same danger: that some worthy government function comes to depend on creating more addicts. And how do you divvy up the revenues? How much goes to offset health consequences? How much goes to enforcement? How do you calibrate taxes so the price of pot is high enough to discourage excessive use, but not so high that a cheap black market arises? All this regulating is almost enough to take the fun out of drugs.

And then there is the issue of drugged driving. Much about the chemistry of marijuana in human beings remains uncertain, in part because the government has not supported much research. So no one has come up with a pot version of the breathalyzer to determine quickly whether a driver is impaired. In the absence of solid research, some legalization advocates insist stoned drivers are more cautious, and thus safer. (Hands up if you want Harold and Kumar driving your taxi. Or piloting your airplane.) On this and much else, Washington and Colorado will probably be making it up as they go, waiting for science to catch up.

And experience tells us they are sure to get some things wrong. New York decriminalized possession of small amounts of pot way back in 1977, with the condition that there be no “public display.” The lawmakers meant to assure that you partied at home, not in the parks or on the sidewalks. They did not envision that this provision would create a pretext for throwing young black and Latino men in jail. When police in New York City stop and frisk, which they do a lot in rougher neighborhoods, they order their targets to turn out their pockets and — whoa, public display, come with us, son! Gov. Andrew Cuomo is promoting an amendment to curb that abuse of power.

On the opposite coast, California demonstrates a different kind of unintended consequences. The state’s medical marijuana law is such a free-for-all that in Los Angeles there are now said to be more pot dispensaries than Starbucks outlets. Even advocates of full legalization say things have gotten out of hand.

“It’s a bit of a farce when you can watch people come out of a dispensary, go around the corner and resell their drugs,” said Gavin Newsom, the lieutenant governor and former San Francisco mayor, who favors legalization. “If we can’t get our medical marijuana house in order, how do we expect voters to deal with legalization?” He is now part of a group discussing how to impose more order on California’s medical marijuana market, with an eye to offering broader legalization in 2016. And, he told me, his state will be paying close attention to Washington and Colorado, hoping somebody can, as Mark Kleiman puts it, “design a system that gets us to ‘orderly’ without getting us to ‘way too stoned.’ ”