"Log in to unsubscribe from this e-mail": annoying, possibly illegal

Everyday, we all open our e-mail inboxes and are greeted by an avalanche of e-mails we don’t want, don’t need, never had to see. The most foolproof way to banish these particular strains of e-mails from our inbox should be unsubscribing, usually via a link in the e-mail itself. But all too often, we find that workflow looks something like this: