The First Circuit has determined that when looking at whether a non-citizen has been convicted of a controlled substance violation, an immigration court should look at the Controlled Substances Act as it was written at the time of the conviction.
The full text of Dor v. Bondi can be found here: https://www.ca1.uscourts.gov/sites/ca1/files/opnfiles/25-1278P-01A.pdf