Authorities said the 38-year-old acknowledged owning the gold-plated handgun after his luggage was searched upon arriving in Miami on a private plane.
A search warrant, first reported by the Miami Herald at the time, said Carter told investigators the gun was a Father’s Day gift.
Carter’s lawyer, Howard Srebnick, said there are legal questions about whether mere possession of a weapon by a felon not judged to be dangerous fits the definition of a crime.
“Carter is charged with possessing a gold-plated handgun in his luggage on a private plane. There is no allegation that he ever fired it, brandished it, used it or threatened to use it,” Mr Srebnick said. “There is no allegation that he is a dangerous person.”
Investigators also reported finding suspected illegal drugs in the luggage, but Carter has not been charged with a drug offence.
An initial court date on the weapons charge is set for December 11 in Miami federal court.
The charge stems from a weapons conviction in New York more than a decade ago, for which he was sentenced to eight months in prison.
Convicted felons are barred under federal law from owning firearms.
As Lil Wayne, Carter has sold more than 120 million records, won five Grammys and numerous other music awards.
He owns a home in Miami Beach and is chief executive of his own record label, Young Money Entertainment.