Final answer:
The U.S. Patent and Trademark Office (USPTO) is responsible for legally enforcing patents.
Step-by-step explanation:
Responsibility for legally enforcing patents rests with the U.S. Patent and Trademark Office (USPTO). The USPTO is the federal agency responsible for granting U.S. patents and registering trademarks. It fulfills the constitutional mandate to secure the exclusive rights of authors and inventors to their respective writings and discoveries. The USPTO plays a crucial role in promoting the progress of science and useful arts by protecting intellectual property.