My clients provide me a .cvs of their customers to add to their email database. Upon uploading that list to me, they check a box on my site stating they received permission to add these customers to their email list (no different than MailChimp or GetResponse).
I then have the list cleaned, upload into Interspire Email Marketer and a welcome autoresponder is sent out from my client. This welcome email tells the customer they're now on the monthly newsletter list, shares a link to previous newsletters and tells the customer they can unsubscribe anytime, including removal links in the header, the footer and a large one in the body that sits between the copy and my client's signature.
So, against the law, not cool or good enough?