Ha! I'm neither a libertarian nor a technoanarchist -- in fact, I'm frequently arguing with those types on HN. But thanks for the laugh.
Laws have room for interpretation, but again, they can't be written in a way that includes legitimate uses as illegal behavior, or the law is worse than useless. Define a rule that says (essentially) "you know spam when you see it", and you end up where pornography is: email marketing will be legal, with random, ineffective, arbitrary restrictions that make business within the domain unseemly and difficult.
Said another way: criminalize unsolicited email and only criminals will send emails.