This is untrue. Subpoenas, wiretapping, and other extrajudicial means can be stopped by legislation that bans them. You can't say in one breath that legislation that enables it (Patriot Act) cannot be undone by more legislation. There are many hurdles required to produce the required legislation, which may not even be broadly supported by the public, but it isn't correct to say "no amount of legislation can stop existing legislation".

A bad legislation is comparatively difficult to revert than a good legislation