What's the legality of spying on our allies? Aren't treaties supposed to be law once ratified? What's the legality of basically giving full system access to al

What's the legality of spying on our allies? Aren't treaties supposed to be law once ratified? What's the legality of basically giving full system access to all NSA data to 'allies' such as Israel with only a footnote in the agreement about using the 'honour system' if they find data in the system that shouldn't be there (e.g. a Senator's data gets caught in the net)? What about the legality of skirting 'no spying on Americans' laws by forming agreements with foreign bodies such that said foreign body readily shares all data it has from spying on Americans (and the NSA does the same thing in kind, sharing data that said foreign body isn't legally allowed to collect on its own).