Legal protection provides a recourse after everything happens. Technological measures don't let it happen in the first place. Or, well, to be more correct - make it significantly harder to happen.
Consider: we can send all our email as non-enveloped postcards and rely on the laws that our correspondence privacy is protected. But for some reason we don't. Why we still send send out our Internet correspondence completely unprotected is beyond me.
It is important that we have laws, so we can get a legal recourse if something goes wrong. But it's extremely naive to think that no one would violate those laws just because they are in place.
Even more, I believe that technological measures must come first. Because if a law comes first, the public relaxes, thinks they're safe now, and few bother about actually putting a lock on the door.