Though many jurisdictions impose penalties for certain blatant acts of copyright infringement and may try to stop certain infringing imports at the border, copyright infringement is still mainly prosecuted through private lawsuits by the copyright holder or their exclusive licensees. When successful, these lawsuits will typically impose monetary damages against the infringer as well as injunctions against future infringing uses.
Many infringement claims involve simple cases of copyright infringement where the copying is obvious. Others, however, are more difficult to resolve because the scope of copyright is not limited to exact copying. It is inevitable that creative works will take inspiration from the culture at large, and it is often challenging to determine when this “inspiration” has crossed the line into infringement, especially in the case of musical works. There also may be a question of whether the allegedly infringed work is even covered by copyright. Works which aren’t covered may include, for example, compilations of facts that lack the requisite creativity to be covered by copyright, or those works that are in the public domain because the copyright term expired.
Copyright notices—often just a simple statement on the work itself of the year protection was acquired and by whom—are not always a good indication of whether a work is covered by copyright because most countries do not require such formalities, and so lack of notice does not mean it is not copyrighted. Courts may also subsequently decide in the context of an infringement suit that the work did not meet the minimum criteria for being covered by copyright, even if the work had been previously registered by a government or private copyright agency. However, copyright notices give at least some indication of whom to contact if permission is needed, and when a copyright will expire, though the copyright terms of pre-existing works are sometimes legislatively extended (as with the Sonny Bono Copyright Term Extension Act) or even restored after expiration (as with the Directive on harmonising the term of copyright protection in the European Union).
To avoid infringement claims, the right to make use of a copyrighted work can be acquired through an explicit contract or license with the author or publisher, through purchasing a lawful copy (which may provide a number of rights to the purchaser, as under the first-sale doctrine), and for certain types of media, statutory licenses (such as for reproducing and recording musical works under U.S. copyright law). Even without going through such channels to get prior authorization for use of the copyrighted material, doctrines such as fair use or fair dealing may provide potentially broad defenses to infringement claims. The failure of a copyright holder to bring a timely lawsuit against known infringers may later block such a claim by establishing an implied license, as may other acts or omissions that could informally signal consent to use the work.
Copyright misuse, the exploitive or restrictive use of a copyright by its legal holder, is sometimes informally called reverse piracy.
Source : wikipedia