Patentees sometimes employ field-of-use licenses, under which they grant the right to use their inventions, but only in specified ways. Field-of-use licensing is often procompetitive, because the ability to provide different licensing terms for different users can encourage broader licensing of inventions. But in recent cases, the Court of Appeals for the Federal Circuit and several district courts have upheld field-of-use licenses that prohibited activities that would otherwise have been permitted by patent law, such as the repair and resale of patented products. By treating any violation of a license agreement as patent infringement, and by upholding license provisions that prohibited previously permitted activities, the courts have allowed patentees to expand the scope of patent infringement liability. This Article describes the dramatic expansion of patent law that has resulted, and it advocates a test that would require a patentee to show that the conduct it challenges would be infringement in the absence of a license before it can seek to make it infringement by license. The Article also briefly compares these effects in patent law to the analogous effects of shrink-wrap licenses and the DMCA in copyright law, and it assesses the potential for similar expansion of patent infringement liability in Europe.