Okpala was a naturalized US citizen when he was convicted of various drug offense. He was subsequently denaturalized, and the Department of Homeland Security sought to use the drug convictions as a basis for removing him. The Fifth Circuit reversed, finding that the convictions were entered while Okpala was a US citizen, and as such, could not be used as predicate offenses to remove him. The court focused on the language of the aggravated felony statute as requiring “an alien” to be convicted after admission..
The full text of Okpala v. Whitaker can be found here:
http://www.ca5.uscourts.gov/opinions/pub/17/17-60391-CV0.pdf