The petitioner was arrested for possession of AB-CHMINACA. While his criminal case pending, AB-CHMINACA was added to the federal controlled substance schedules. The petitioner subsequently pled guilty. He was later charged with inadmissibility for the conviction. He challenged that finding, arguing that penalizing him for conduct involving the substance prior to the addition of the substance to the CSA was impermissible retroactive. The Fifth Circuit agreed.
The full text of Lopez Ventura v. Sessions can be found here:
http://www.ca5.uscourts.gov/opinions/pub/17/17-60529-CV0.pdf