I'm aware of Mr. Akin's argument as follows:
Yet the penalty was used so seldom that it was removed from the 1983 Code of Canon Law. This means that today the penalty of anathema does not exist in Church law. The new Code provided that, "When this Code goes into effect, the following are abrogated: 1º the Code of Canon Law promulgated in 1917 . . . 3º any universal or particular penal laws whatsoever issued by the Apostolic See, unless they are contained in this Code" (CIC  6 §1). The penalty of anathema was not renewed in the new Code, and thus it was abrogated when the Code went into effect on January 1, 1983.(source)
The problems with that type of argument are:
1) Where was anathema mentioned in the 1917 Code? I've perused that code and couldn't find it. Perhaps I overlooked something?
2) A penalty and a penal law are not the same thing.
If that's all Mr. Akin has, his argument seems exceptionally weak.