Limitations and exceptions.

In many jurisdictions, copyright law makes exceptions to these restrictions when the work is copied for the purpose of commentary or other related uses. United States copyright law does not cover names, titles, short phrases or listings (such as ingredients, recipes, labels, or formulas). However, there are protections available for those areas copyright does not cover, such as trademarks and patents.

Idea–expression dichotomy and the merger doctrine.

The idea–expression divide differentiates between ideas and expression, and states that copyright protects only the original expression of ideas, and not the ideas themselves. This principle, first clarified in the 1879 case of Baker v Selden, has since been codified by the Copyright Act of 1976 at 17 U.S.C. § 102(b).

The first-sale doctrine and exhaustion of rights.

Copyright law does not restrict the owner of a copy from reselling legitimately obtained copies of copyrighted works, provided that those copies were originally produced by or with the permission of the copyright holder. It is therefore legal, for example, to resell a copyrighted book or CD. In the United States this is known as the first-sale doctrine, and was established by the courts to clarify the legality of reselling books in second-hand bookstores.

Some countries may have parallel importation restrictions that allow the copyright holder to control the aftermarket. This may mean for example that a copy of a book that does not infringe copyright in the country where it was printed does infringe copyright in a country into which it is imported for retailing. The first-sale doctrine is known as exhaustion of rights in other countries and is a principle which also applies, though somewhat differently, to patent and trademark rights. It is important to note that the first-sale doctrine permits the transfer of the particular legitimate copy involved. It does not permit making or distributing additional copies.

In Kirtsaeng v John Wiley & Sons Incorporated, in 2013, the United States Supreme Court held in a 6–3 decision that the first-sale doctrine applies to goods manufactured abroad with the copyright owner's permission and then imported into the US without such permission. The case involved a plaintiff who imported Asian editions of textbooks that had been manufactured abroad with the publisher-plaintiff's permission. The defendant, without permission from the publisher, imported the textbooks and resold them on eBay. The Supreme Court's holding severely limits the ability of copyright holders to prevent such importation.

In addition, copyright, in most cases, does not prohibit one from acts such as modifying, defacing, or destroying one's own legitimately obtained copy of a copyrighted work, so long as duplication is not involved. However, in countries that implement moral rights, a copyright holder can in some cases successfully prevent the mutilation or destruction of a work that is publicly visible.