Patent infringement is an invasion of a patentee's right to make, use, or sell a patented invention. Because patent infringement actions involve an examination of the claims of an issued patent and comparison of the patented article and the accused article, experts generally are required. The complexity of patent law and of the technology underlying most patents makes patent litigation extremely costly. Patent infringement can lead to damages in the millions.
Before a trademark registration is issued by the Patent and Trademark Office (PTO), the trademark is published in the Official Gazette so that parties who believe they may be damaged by registration of the mark can oppose registration. Similarly, after a trademark is registered, it can be canceled upon the petition of one who can prove that he or she is damaged by continued registration of the mark. No analogous procedures exist for opposing or canceling patents in the United States. Nevertheless, any person (including the patentee) can file a request with the PTO that it reexamine the patent on the basis of prior art (consisting of patents or printed publications) the person believes has a bearing on the patentability of any claim. A request for reexamination can be made at any time during the life of the patent. The reexamination fee is $2,520. There is no reduced fee for small entities.