Law enforcement agencies may often use informant and undercover operators in an effort to gather evidence in a criminal investigation. Undercover sting operations are used in a wide variety of contexts, and at just about any level of law enforcement. Police may send an undercover operative to create a drug transaction with an alleged suspect.
Officials in East Baton Rouge Parish arrested a number of men dating back to 2011 after using undercover stings to gather evidence in alleged sex crimes. The issue has garnered national attention--not because of the sting operation--but because the arrests were not authorized under the law in the first place. The government officials were setting up sting operations to charge men with sex crimes under a law that is unconstitutional.
The East Baton Rouge Parish sheriff has made a public apology concerning the whole mess. The arrests began occurring in 2011 from the sting operation. But, the anti-sodomy law that authorities were seeking to enforce (while still on the books in Louisiana) was ruled unconstitutional by the United States Supreme Court about a decade ago--long before law enforcement set up the stings.
An account in the Advocate says that the issue in East Baton Rouge has created a public debate over the unconstitutional law. While prosecutors reportedly declined to prosecute the sex crimes, the story shows how criminal defense arguments about the constitutionality of a law are not mere technicalities. Our system generally allows the legislature to define crimes--but not without limitation under the Constitution.
Source: The Advocate, "Gautreaux issues apology, begins push to have La. law erased," Jim Mustian, July 31, 2013