Jennifer Hendricks has posted this draft on SSRN. Here is the abstract:

Earlier this year, Maryland became the first state to adopt the Agreement Among the States to Elect the President by National Popular Vote. If states sign on to this agreement to control the Electoral College, they will all pledge their electoral votes to the presidential candidate who wins the national popular vote, without regard to which candidate won in each individual state. The compact would effectively supersede the Electoral College and implement popular election of the president without amending the Constitution. Political supporters of the Agreement have been curiously reticent to discuss the validity of the Agreement under Article I, section 10. Although some similar proposals would be invalid under section 10, the Agreement adopted in Maryland does not abuse the structure of the Electoral College, nor does it disrupt the balance of power among the states or between the states and the national government. The Agreement is therefore permissible and probably does not even require congressional consent.

Derek Muller reached a contrary conclusion in an article in the latest issue of the Election Law Journal.