according to the snowden documents it is quite obvious that if the US government had a backdoor then the UK government would have one through five eyes

It’s possible that the back door already exists, and they already have it. So if they had conducted unlawful surveillance using these methods, then they may have to come up with some plausible explanation as to how they got that information legally. You could imagine a scenario where there is no plausible explanation for how the information could have been legally obtained. If they codify the use of the back door into law, then there is no need for all this theater.

One of my favorite conspiracy theories is that this is what the CIA Stargate program was. You don’t leak the existence of informants or satellites because you just got the information from “a psychic“.

Exactly they built one for the Chinese government. It's not if they have a back door it's who gets to use it