The Copyright Act provides a way.
17 USC 512 http://www.law.cornell.edu/uscode/text/17/512 is the relevant statute and is known as the DMCA (Digital Millenium Copyright Act). It provides a "safe harbor" for Internet websites hosting third party content that the host does not control for profit. The Act provides first for a "takedown" notice from a person, who does not have to be the copyright owner, to the website owner putting the website owner on notice that content on the website infringes the rights of a person and asking that the infringing content be removed. The website owner must remove the content in response to a proper takedown notice or risk losing the safe harbor protection of the DMCA. Nearly all website owners want that safe harbor and so comply. The website owner then notifies the person posting the content that the content has been removed pursuant to the DMCA and that the poster has an opportunity to provide a counter notice stating the content does not infringe and giving the contact information for the poster so the poster can be sued for copyright infringement. If the poster files that counter notice the material is reposted and the sender of the take down notice is so informed and provided with a copy of the counter notice. This immunizes the website from further liability in the matter. The person alleging infringment must now take the matter to court to get a court order of removal of the infringing material.
Read the statute at http://www.law.cornell.edu/uscode/text/17/512 to see the detailed provisions and if you want to have this done, it is best to see an Intellectual Property Attorney as there may be other avenues to explore, such as sending the infringer a CDL (cease & desist letter) or even suing the infringer without any prior steps.