The legal monopoly granted by a copyright allows the author of a work to profit from that work to the exclusion of all others. It also allows him to assign his copyright to someone else, such as a publishing company. This system not only motivates authors to create original works in the hopes of becoming wealthy, it also allows established authors to rely on royalty income so that they can focus exclusively on their craft without being distracted by the necessity of earning a living doing something else. These incentives in turn benefit society by increasing the output of creative works for all to enjoy.
The copyright monopoly necessarily restricts the use of copyrighted works to the owner of the copyright — normally the author, the author’s employer, or an assignee such as a publisher or a record company. This prevents the unhindered distribution of these works to the public until the copyright expires. This monopoly endures for various time periods, depending on the date of creation of the work and the identity of the initial copyright holder. A work authored by a individual (rather than a corporation) in 2011, for example, will be copyrighted for 70 years after the death of the author. This allows an artist to exercise “dead hand control” over his copyright through his heirs; the works of Elvis Presley, for example, are still protected by copyright even though he died in 1977.
“Fair use” is an exception to copyright restriction that allows anyone to use a small portion of a copyrighted work for a socially beneficial purpose such as education, criticism or parody. The fair use exception mitigates the harshness of the copyright monopoly. The difficulty in applying it, however, lies in defining just how much use constitutes a “small portion.” No clear legal definition exists – how much use is "fair" depends on a number of factors including the size of the portion used compared to the size of the entire work, and the likelihood that the use will cause economic damage to the copyright holder. This provides little guidance to someone who, for example, wishes to include a clip from a copyrighted film in a video to be uploaded to YouTube.
U.S. copyright law is defined by a number of statutes, including the Copyright Act and the Digital Millennium Copyright Act. The Copyright Act has been amended many times over several decades, resulting in a complex matrix of legal protections for works created at different times. For example, a copyright holder was once required to affix a copyright notice to his work to be entitled to protection. Works first published after March 1, 1989, however, are protected even without a copyright notice. Different legal protections also apply to registered and unregistered works; only authors of works registered with the U.S. Copyright Office, for example, may collect damages without proving economic harm. Although a work of authorship created in one country is entitled to copyright protection in other nations that have entered into copyright treaties with the U.S. (most of the world’s nations), this protection is subject to local copyright law, which differs in many cases from the protections offered by U.S. law.