Talking about a future in which AVs are allowed to go as fast as physically possible seems irrelevant when we're talking about current policy and infrastructure, in which AVs have to live in a world with majority manually-operated vehicles, driven by people who do speed, but are also punished for going over the speed limit.
An autonomous vehicle should also be pulled over and ticketed for operating unsafely. At this point in time the driver is still liable for the actions of the car and is required to monitor the autonomous system and takeover if necessary. However like a human it should have some discretion in interpreting the law. Should it go 120 in a 60 zone... definitely not but if it thinks it can do 38 in a 35? That sounds fine.