In that sense, it was different than a lot of the 14th Amendment cases in which the judiciary finds that a state statute is unconstitutional. In Martin, the court was just applying a statute that was passed by Congress. For its part, Congress claimed it was acting under the constitutional authority granted to it by both the Fourteenth Amendment and the commerce clause.
Reminds me of the paragraph in :
http://www.freerepublic.com/forum/a38ae1fc86628.htm
Titled: If You Liked the Commerce Power. . .