I'm typically against regulation of most things, but I lean towards regulation of aggressive dog breeds. Pitbulls, Rottweilers, Dobermans, German Shepherds, etc. can be the best of companions if trained properly but also can be human killers if trained to be guard dogs or are not properly trained. I think background checks on the humans who wish to own an aggressive dog breed is appropriate and ownership should be prohibited for new dog owners or humans with a history of violent behavior to own one.
There should also be required regular behavioral inspections of the aggressive breed and if a dog fails inspection the owners lose the dog and are no longer allowed to own an aggressive breed. Depending on the level of aggressiveness, the dog either gets put down or rehabilitated under new ownership.
...Just my two pennies on the topic...