Due to the international nature of the Internet, Internet pornography carries with it special issues with regard to the law. There is no one set of laws that apply to the distribution, purchase, or possession of Internet pornography. This means that, for example, even if a pornographer is legally distributing pornography, the person receiving it may not be legally doing so due to local laws.
So it states that the pornography itself is not illegal but the person viewing it in certain communities could be.
Sort of like the use of radar detectors in some states is illegal but it is not illegal to own them in those states.