I think he already dropped the code when he killed Hannah's father. At the very least, he modified it or bent it. The guy was a slimeball but he didn't meet the code.
That whole episode was about Dexter acknowledging that his "dark passenger" didn't really exist. It's been him all along. He decides who dies. And he accepts the fact that he maybe doesn't "need" to kill... but he wants to. He enjoys it.

I think Clint McKay's death shows that, going forward, Dexter is capable of killing almost anyone if he wants to. If he can justify it. Clint threatened Hannah. Dexter loves Hannah. Clint goes into the ocean. Laguerta threatens Deb (assuming here that she will find out Deb planted that evidence on Doakes last show) . Dexter loves Deb. Laguerta goes into the ocean.