[berkes]

I agree that much clearer constraints and less wiggle room would be better.

But imposing technical solutions in laws has hardly ever worked. Because these are almost always much easier to circumvent.

E.g. your suggestion to "honor browser headers" would be easy to circumvent by not having a browser - native apps, alt clients, etc. Google would easily track almost everything they do now through android, play services, email, docs, etc. And such implantation details inevitably get outdated. E.g. in The Netherlands we have a law that forbids, with severe punishment, that you read people's paper post. If only lawmakers hundreds of years ago had abstracted this to "correspondence" rather than paper mail in envelopes, it would've applied to email and probably all network traffic.