A favorite trick of warez sites, this so-called defense against The Man usually cites the Internet Privacy Act (or occasionally the Telecommunications Act), signed by Bill Clinton in 1996 or thereabouts. The Act, which (at least in the case of the Internet Privacy Act) doesn't exist, is generally quoted like this:
By entering this website, you agree that you are not in any way affiliated with any government, police, ANTI-Piracy group, RIAA, MPAA, IDSA or any other related group, and that means that you CANNOT enter this website. By entering and not agreeing to these terms you are violating code 431.322.12 of the Internet Privacy Act signed by Bill Clinton in 1996, and you cannot threaten or bring suit against this site's ISP(s) or owners.
This fallacy seems to base itself on the Are you a cop? principle, in which people believe that undercover cops are required to be totally truthful and in posession of a warrant before being deceitful in any way, lest they be found guilty of entrapment. Of course, if this were true, there wouldn't be much point in having undercover cops (or an cybercrime division) to begin with, would there? Unfortunately, warez d00ds are rarely high enough on the good ol' Cognitive Thought Totem Pole to realize this for themselves.
On the other hand, this produces a false sense of security, which will make their faces all the more priceless when COPS starts airing videos of busts on pimple-faced 13-year old 31337 h4x0rz.