I think it would and should be possible to use products run by a foreign country if that country respects the rule of law and has decent oversight in place (both on paper and in practice). But the US with its National Security Letters and secret FISA courts is not that kind of country.
Can you explain how "National Security Letters and secret FISA courts" violate US laws? If they don't violate US laws can you explain how they're examples of how the US doesn't' respect the rule of law? If you mean that the US doesn't respect the laws of other separate sovereign nations, isn't that how the system works?
> If they don't violate US laws can you explain how they're examples of how the US doesn't' respect the rule of law?
They are special exceptions to the normal process of law that favour particular actors. Rule of law means that the processes of law must be consistent and public, and fair to all sides; people need to be able to tell their stories publicly in order to be able to find relevant witnesses, for example.
