The drug cases all came out of the U.S. District Court in North Mississippi since 2010.
The 5th U.S. Circuit Court of Appeals on Wednesday returned the cases of James Hicks, Samuel Pettis and Larry Shoumaker to the Mississippi court. Willie Lee Fields case was returned earlier this month.
A fifth case — that of Desmond Burnett — is pending before the 5th Circuit.
The U.S. Supreme Court ruled in June that people who committed crack cocaine crimes before more lenient penalties took effect and received their prison sentence afterward should benefit from the new rules.
The Supreme Court said the courts should have used the new law for sentencing.