The anticircumvention liabilities are independent of any rights, remedies , limitations , or defenses to copyright infringement. The courts have explicitly treated fair use as independent of, and therefore inapplicable to, any anticircumvention limitation. “clearly and simply clarifies that the DMCA targets the circumvention of digital walls guarding copyright material, as well as trafficking in circumvention tools, but it dose not concern itself with the use of those materials after circumvention has occurred. As a result, infringement of one of the exclusive rights included in copyright is not necessary to, and is independent of, a finding of sufficient liability to impose civil or criminal penalties for anticircumvention violations. This means that defenses to copyright infringement are not directly applicable to claims of violation of the anticircumvention provisions. In addition , constitutional challenges to the anti circumvention provisions have not been successful. As explained below , narrow limitations for, and exemption from, anticircumvention liability are provided in the statute.