Colorado No-Spam?

BeSpacific notes that the Colorado legislature is considering a bill that would create a no-spam list strongly resembling the Colorado No-Call List for telephone solicitation.

I'm a huge fan of the Colorado No-Call List. I haven't received a telemarketing call since the end of October, except from a company I already do business with (whom the law exempts from its restrictions), and even then only twice. Yet I suspect that doing the same for e-mail would be much harder to police, because the sources of spam email are much more easily faked. It could have different First Amendment free speech clause implications, too, since junk email is arguably less intrusive than the ringing of a telephone during dinner. Even the constitutionality of the No-Call List law has not yet been fully resolved -- at least, not that I've heard.