That’s not quite right. The Bill of Rights originally only applied to the federal government, until after the civil war when the 14th amendment was passed. Since then the clause in that amendment saying no one can be deprived of life or liberty without due process has been interpreted to mean most of the bill of rights also applies to the states. This ruling said as much for the 8th amendment prohibitions on excessive fines.
Thomas just wanted to use a different clause of the 14th amendment to achieve the same outcome.
Thomas just wanted to use a different clause of the 14th amendment to achieve the same outcome.