Yeah, this is common joke, especially when you feel ambivalent.
Examples:
"Do you want to go out for dinner tonight? Or should we stay in and save money?"
"Do you want cake or ice cream for dessert?"
"Should we prioritize this bug fix or focus on hitting our release target?"
Somebody might reply with tongue in cheek, "Yes", to indicate they agree with both parts, want both things, it's not a simple choice, etc.
FWIW, I encounter it more with older people. As a kid, I heard it often from uncles and grandparents.
The joke is in treating the "or" as the Boolean operator and collapsing it into a yes-no question.
Thus, the answer would be "no" if and only if legalization has had no effect whatsoever. As the asking of the question implicitly assumes that there has been an effect, answering yes therefore responds to the question in a very literal, truthful way, without actually conveying any new information.
This is my favorite way to punish a poorly structured interrogatory. It forces the follow-up question, "Which one?" Which can then be answered with "both."
Some people say that there are no stupid questions, but clearly, some questions are more intelligent than others.
Don't you hate it when you ask someone if they want coffee or tea and they say "yes"?
I mean, strictly speaking they answered the question. They do want a coffee or a tea. They just haven't yet specified which one they would like most...
~Don't you hate it when you ask that question out of curiosity, and then the person you asked gets all mad that you didn't give them either coffee or tea afterward?~
The question has several possible responses. "No, thank you," means the person wants neither coffee nor tea. "Coffee, please," and "tea, please" mean just what you think. "Yes, please," means that either coffee or tea would be acceptable, and the respondent is indifferent to which one.
This usually means "I'll take one of whatever you're having," and is probably intended to be less burdensome to the host, by allowing them to choose what they would prefer to serve rather than forcing them to defer to their guest.
Of course, the person might be trying for a cheap laugh rather than politeness. In that case, it would be appropriate to wait a beat, chuckle, optionally make a flirtatious gesture (such as a wink or arm touch), then ask "So either one is fine?"