In the case of Jose Antonio Lopez v. Alberto R. Gonzales, Attorney General in 2006, the U.S Supreme Court ruled that a South Dakota state drug conviction did not constitute an "aggravated felony" under federal immigration law and therefore could not be used as grounds for automatic deportation. The court held that while Mr. Lopez's crime was indeed serious, it did not meet the specific criteria set out by Congress to define an aggravated felony - namely that it must involve trafficking in illicit drugs on a large scale or other similarly severe offenses such as murder or sexual abuse of a minor. This decision clarified how state convictions should be interpreted under federal immigration law and provided important protections for immigrants who have been convicted of less serious crimes at the state level.

In the dissenting opinion for Jose Antonio Lopez v. Alberto R. Gonzales, Justice Thomas argued that the majority misinterpreted federal immigration law and improperly expanded its scope to include state drug convictions as grounds for deportation. He contended that Congress intended a narrow interpretation of "aggravated felony," which should only encompass serious crimes such as murder, rape or sexual abuse of minors, not minor drug offenses like those committed by Mr. Lopez in South Dakota. The justice also criticized the majority's reliance on a 1996 amendment to justify their broad interpretation, arguing it was irrelevant since it did not specifically address whether state felonies could be considered aggravated felonies under federal law.