Firstly you were born on a patch of land that imposes its own laws on you. Did you sign a contract to say you would adhere to those laws? This is all about power and control over less powerful innocent people being treated like sleepy idiots. So to answer your question, out smart them to win, and then you will find they play dirty and illegally, against the spirit of the law they claim to uphold. 5 Eyes best demonstrates this by circumventing domestic laws, they dont have the intelligence to win the argument in their own courts. This also tells you that you can out smart them so get thinking, this is an intelligence game.

i am so opposed to mass surveillance that if i could snap my fingers and make both Ft Meade and Cheltenham into craters, i would have zero hesitation. so i am no FVEYS shill. but i still care about the historical accuracy of mass surveillance.

in the Snowden leaks, there was a GCHQ document about their policies for targetting US Persons using data shared with them from NSA. GCHQ is not allowed to indiscriminantly spy on US Persons. the document, marked classified as STRAP1, clearly orders GCHQ to apply US laws when targetting US Persons. which means "reasonable, articulable suspicion" before firing up XKEYSCORE and searching for everything a US Person has done in their life.

sadly, the reverse is not the same, since the UK has very weak privacy laws compared to the US. NSA can search for anything about any UK citizen without needing some form of probable cause. the Official Secrets Act and RIPA makes the UK into a quasi-dictatorship IMHO, which explains why we see the native population of the UK being so heavily subjugated by their Lords and Royals.

part of the SIGINT sharing agreement between NSA and GCHQ is that data will only be shared as long as these rules are enforced. so the myth that the FVEYS is a backdoor to circumvent the law and allow foreign intel to mutually spy on each other's domestic populations is a myth.

however, this assumes the FVEYS actually obey the rules in this document. how would we know if they dont? impossible for us uncleared civilians. for all we know, there are more layers of secret laws that allow FVEYS to ignore any and all of the checks and balances intended to limit their abuse of the SIGINT system.

that's the problem with secret laws. once you have them, nobody can trust anything about your entire legal system and you become a tyranny.