Well, perhaps not essential. But some very good academic writing on the constitutionality of the Affordable Care Act, for those so inclined. I have been meaning to compile a list for quite a while--and please let me know if I have missed something important. (Presented in alphabetical order, by author.)
* Jonathan H. Adler, Cooperation, Commandeering, or Crowding Out? Federal Intervention and State Choices in Health Care Policy.
* Akhil Amar, The Lawfulness of Health-Care Reform.
* Jack Balkin, Commerce.
* Randy E. Barnett, (1) Commandeering the People: Why the Individual Health Insurance Mandate is Unconstitutional, and (2) Jack Balkin's Interaction Theory of "Commerce."
* Patrick McKinley Brennan, The Individual Mandate, Sovereignty, and the Ends of Good Government: A Reply to Professor Randy Barnett.
* A. Christopher Bryant, Constitutional Forbearance.
* Tom Campbell, Severability of Statutes.
* Eric R. Claeys, Obamacare and the Limits of Judicial Conservatism.
* Robert Cooter and Neil S. Siegel, (1) Collective Action Federalism: A General Theory of Article I, Section 8, and (2) Not the Power to Destroy: A Theory of the Tax Power for a Court That Limits the Commerce Power.
* Katherine Mims Crocker, Securing Sovereign State Standing.
* Kenneth Cuccinelli, III, E. Duncan Getchell, Jr., and Wesley G. Russell, Jr., State Sovereign Standing: Often Overlooked, But Not Forgotten
* Michael C. Dorf, (1) The Constitutionality of Health Insurance Reform, Part I: The Misguided Libertarian Objection, and (2) The Constitutionality of Health Insurance Reform, Part II: Congressional Power.
* Tobias A. Dorsey, Sense and Severability.
* Richard A. Epstein, Impermissible Ratemaking in Health-Insurance Reform: Why the Reid Bill is Unconstitutional.
* Brian D. Galle, (1) Conditional Taxation and the Constitutionality of Health Care Reform, and The Taxing Power, the Affordable Care Act, and the Limits of Constitutional Compromise.
* Lawrence O. Gostin and Kelli K. Garcia, Affordable Care Act Litigation: The Supreme Court and the Future of Health Care Reform.
* Mark A. Hall, (1) Commerce Clause Challenges to Health Care Reform, and (2) The Factual Bases for Constitutional Challenges to Federal Health Insurance Reform.
* Edward A. Hartnett, Facial and As-Applied Challenges to the Individual Mandate of the Patient Protection and Affordable Care Act.
* Daniel Jacob Hemel, How to Reach the Constitutional Question in the Health Care Cases.
* Nicole Huberfeld, (1) Federalizing Medicaid, and (2) Post-Reform Medicaid Before the Court: Tension Between Reinvention and Path Dependence.
* Lawrence Jacobs and Suzanne Mettler, Structural Framing: Health Care reform and changing American Politics.
* Erik M. Jensen, The Individual Mandate and the Taxing Power.
* Douglas A. Kahn and Jeffrey H. Kahn, Free Rider: A Justification for Mandatory Medical Insurance Under Health Care Reform?
* Andrew Koppelman, (1) Bad News for Mail Robbers: The Obvious Constitutionality of Health Care Reform, and (2) Bad News for Everybody: Lawson and Kopel on Health Care Reform and Originalism.
* Kurt T. Lash, 'Resolution VI': The Virginia Plan and Authority to Resolve 'Collective Action Problems' Under article I, Section 8.
* Gary Lawson and David B. Koppel, (1) Bad News for Professor Koppelman: The Incidental Unconstitutionality of the Individual Mandate, and (2) Obamacare in Wonderland.
* Renee M. Landers and Patrick A. Leeman, Medicaid Expansion Under the 2010 Health Care Reform Legislation: The Continuing Evolution of Medicaid’s Central Role in American Health Care.
* Elizabeth Weeks Leonard, (1) Rhetorical Federalism: The Value of State-Based Dissent to Federal Health Reform, and (2) The Rhetoric Hits the Road: State Resistance to Affordable Care Act Implementation.
* Philip Levitz, A Modern Fiduciary Theory of the Necessary and Proper Clause.
* Ruth Mason, Federalism and the Taxing Power.
* Ian Millhiser, Worse Than Lochner.
* Abigail Moncrieff, (1) The Freedom of Health, (2) Safeguarding the Safeguards: The ACA Litigation and the Extension of Structural Protection to Non-Fundamental Liberties, and (3) Cost-Benefit Federalism: Reconciling Collective Action Federalism and Libertarian Federalism in the Obamacare Litigation and Beyond.
* Abigail Moncrief and Eric Lee, The Positive Case for Centralization in Healthcare Regulation: The Federalism Failures of the ACA.
* Robert G. Natelson and David Kopel, Commerce in the Commerce Clause: A Response to Jack Balkin.
* Gregg D. Polsky, Reconstructing the Individual Mandate as an Escrow Account.
* Richard Primus, How the Gun-Free School Zones Act Saved the Individual Mandate.
* Neomi Rao, American Dignity and Healthcare Reform.
* Theodore W. Ruger, Plural Constitutionalism and the Pathologies of American Health Care.
* Stephen E. Sachs, The Uneasy Case for the Affordable Care Act.
* Neil Siegel, (1) Free Riding on Benevolence: Collective Action Federalism and the Individual Mandate and (2) Four Constitutional Limits that the Minimum Coverage Provision Respects.
* Ilya Shapiro, A Long, Strange Trip: My First Year Challenging the Constitutionality of Obamacare.
* Sam Singer, Defending the Affordable Care Act: What the Justice Department Can Learn from the Legal Academy.
* Ilya Somin, (1) Taking Stock of Comstock: The Necessary and Proper Clause and the Limits of Federal Power, and (2) A Mandate for Mandates: Is the Individual Health Insurance Mandate Case a Slippery Slope?
* Peter J. Smith, Federalism, Lochner, and the Individual Mandate.
* John T. Valauri, Baffled by Inactivity: The Individual Mandate and the Commerce Power.
* Steven J. Willis and Nakku Chung, (1) Of Constitutional Decaptitation and Healthcare, (2) Oh Yes, the Healthcare Penalty Is Unconstitutional, and (3) Credits vs. Taxes: The Constitutional Effects on the Health Care Reform Debate.
* Kevin Walsh, (1) The Ghost that Slew the Mandate, and (2) The Anti-Injunction Act, Congressional Inactivity, and Pre-Enforcement Challenges to Section 5000A of the Tax Code.
* Jennifer Wriggins, Is the Health Insurance Individual Mandate 'Unprecedented'? The Case of Auto Insurance Mandates.
* Corey Rayburn Yung, The Incredible Ordinariness of Federal Penalties for Inactivity.
* Rebecca E. Zietlow, Democratic Constitutionalism and the Affordable Care Act.
* A Healthy Debate: The Constitutionality of an Individual Mandate, U. Pa. L. Rev. PENNumbra.
* The Constitutionality of the Affordable Care Act, SCOTUSblog symposium.