"A Colorado legislative committee has passed a bill that would
require spammers to tag unsolicited email with a special subject
'[Senders must] use the exact characters 'ADV:' ... as the
first four characters in the subject line of an unsolicited
commercial electronic mail message,' reads the so-called Colorado
Junk Email Law, House Bill 1309."
"The House Business Affairs and Labor Committee passed the bill
Thursday by a vote of 10-2, strengthening the law by adding
politicians and nonprofit organizations to the list of those who
must use the label in their promotional email. The bill goes next
to Colorado's full house for debate."