Should we consider the simpler cases first? And define fundamental principles?

Does the government have any right to demand access to telephony billing records (which show who calls and texts whom). Should phone companies even keep these records and be allowed to create bills from them? (i.e. they could count calls, or minutes, or have a fixed fee, or a mix, rather than making a record of who called whom). All transactions between two individuals mediated by a third have this trust and privacy element. At times process (aided by technology) could insure there are no records beyond days if not seconds – which suggests a return to depending on human testimony and an elimination of records, written and otherwise, as evidence in court proceedings.

Ditto for financial records. And shipping records.

What about non-U.S. persons? And U.S. persons in other countries? Does their presence in another country subject them to the other countries rules?