Ten years after the passage of the 'Mental Health Parity and Addiction Equity Act' (MHPAEA), parity between mental health/substance use disorders and medical/surgical benefits remains elusive. This note describes the statute's cooperative federalist framework and analyzes enforcement data and settlement documents demonstrating the role of states in prospective enforcement. In comparing the MHPAEA to other cooperative statutes, it concludes that MHPAEA compliance could be improved by expanding private rights of action, promoting stakeholder collaboration, utilizing conditional spending, and allowing for waivers. The note also renews calls for consumer education, clarifying regulations, and proactive enforcement by federal agencies and states.