system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is the USA PATRIOT Act still functioning, despite constant criticisms about its unconstitutionality, as in why hasn't the Supreme Court overturned it yet?
gpt
In order to challenge the constitutionality of a law you have to have standing to do so - the simplified version of that is you have to be able to prove the law has harmed you or infringed on your rights or (in some rare cases) that it is likley to do so.  

So far most of the challenges to the USA PATRIOT Act have been rejected on standing grounds, the Court finds that people lack any proof that they have been harmed by the law.  Since the most controversial provisions of the law have to do with what the government can do in secret, it turns out to be very hard to prove you have been harmed by the law (and when you can, that evidence may be in admissible on state secret grounds).  So you lack standing.

TL:DR if you can't prove you've had your rights violated because the violation was secret, you can't challenge the violation because you can't prove it happened.