Double criminality (also known as dual criminality) is a requirement in the extradition law of many countries. It states that a suspect can be extradited from one country to stand trial for breaking a second country's laws only when a similar law exists in the extraditing country.
Example: if Country A has no laws against blasphemy, double criminality could prevent a suspect being extradited from Country A to face blasphemy charges in another country.
In the USA
Double criminality is a requirement in extradition procedures from the United States of America, as extradition is allowed only for offenses alleged as crimes in both jurisdictions.
References
Double criminality Wikipedia(Text) CC BY-SA