I sent a campaign out to a list last month, and would like to send the same campaign out to the same list this week. Is this legal? Will I experience a backlash of unsubscribers as a result? Thanks in advance!
I can't see any reason this would be illegal, assuming you had permission to send to them in the first place.
I can, however, see many reasons why you should refrain from doing it. A backlash of unsubscribers is one of them.
Could you explain what you want to accomplish by resending it?
If you want to send it to everyone who has subscribed since your last campaign, you can send it to a segment consisting of subscribers who have opted in since the date you sent it.
If you want to send it to everyone who didn't open it the last time, you can send it to a segment consisting of those subscribers.
If there's another reason you'd like to do this, you could post it here, and someone should be able to advise.