This would be a legally enforceable replacement for the utterly-failed “Do Not Track” (DNT) header, that is gaining traction.
The spec is simple enough for us to implement. All it needs is a pref or the user to set, and depending on that have a single boolean field on the Navigator object (why are people still insisting on using this?...) set to true if the header is sent, false if not.
The header is a simple
Sec-GPC: 1 if set, or omitted if not.
It is then up to the server to adhere to the policies it needs to enforce according to this flag.