UCE is legal in the U.S. with the condition that a functional opt-out URL be provided in all instances of the UCE. (Such a URL is an email validator, alas. This actually makes things easier for UCE specialists, since there is no particular requirement to remove the email address from other email lists.)

However, the Federal law explicitly legalizing UCE is fairly recent (late 2001?). Violations are the domain of the U.S. FTC.