Andrew McCarthy and Heather Mac Donald continue their polite and interesting (dare I say elegant?) debate on The Corner over what preemption means with regard to the Arizona immigration law. (You can get the links to their previous posts here.) In the latest installment, McCarthy sets the stage for further discussion:

Heather has good cause to be unsure of how today’s federal courts will resolve the preemption question she posits – in a nutshell: Can a state, consistent with the Constitution, enforce a state-law immigration penalty that is consonant with federal statutory law but contravenes a presidential policy of non-enforcement? My confident assertion that a state can do so is based on my understanding of the Constitution’s division of federal and state power, rather than on how the whimsical federal courts may choose to “evolve” that division.

As Heather suggests, I do draw a bright-line between executive enforcement policy (which is politics) and congressional statutes (which are law). On this point, the foundational disagreement I have with Heather is about the Constitution. Heather writes: “In so exercising his discretion, a president has not entered into some extra-constitutional ‘political’ territory, as Andy seems to suggest; he is operating within his constitutional legal powers.” Respectfully, I think this misinterprets the Constitution which is foremost a political document, not a legal one.

This is fascinating stuff-and a model of civil discourse. I can’t wait to see Heather’s next post.