The United States Supreme Court ruled in Carachuri-Rosendo v. Holder, Case No. 09-60, 560 U.S. ___, (June 14, 2010)that a second or subsequent offense for simple possession of a controlled substance is not an aggravated felony unless the offense was actually prosecuted on the basis of a prior conviction. This decision establishes that if there is no finding of a prior conviction in the record of the subsequent conviction, the latter conviction may not be deemed an aggravated felony. Even where there is some finding of a prior conviction, the conviction must adhere to the requirments of the federal recidivist felony statute to be used in a deportation proceeding.
A great article on this case is by Joy Sanders, “U.S. Supreme Court Rules Noncitizens with Two or More Misdemeanor Possession Convictions are not Automatic Aggravated Felons”, The Houston Lawyer, page 47-48, July 2010.