A more realistic option would be to institute a strong audit process. Anytime personal data is viewed or matched against some criteria, it would be logged. By default, those logs would be available after something like a few years, unless there's an ongoing investigation (and that extension would be logged along with who/why it was authorized).<p>The only way something like this could even work is if there was a completely separate government agency that was both empowered and motivated to be the counterweight against warrantless surveillance. Unfortunately, I have no idea how this could ever happen.