"The Congress shall have power ... to promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries." This section of the Constitution instructs the Congress to establish copyright and patent laws. Copyright laws protect artistic works such as books, paintings and motion pictures from unauthorized copying. Patent laws protect inventions from being copied without permission of the inventor..
Over the past decades Congress has repeatedly extended the length of copyright, primarily to protect the copyrights of companies such as Disney who did not want the copyright of Mickey Mouse extended. The extension has been challenged claiming that the lengthy and effective copyrights that last forever violate the inention of the framers in writing for a "limited time". The courts have decided that it is up to Congress to decide the meaning of "limited time".