This battle for the Constitution was forced upon defenders of limited government by Congress in 2010, when it insisted in the health-care bill that it was constitutional to require all Americans to purchase insurance or pay a fine. Lawmakers argued that this mandate was justified by the Constitution’s commerce and “necessary and proper” clauses. Had we not contested this power grab, Congress’s regulatory powers would have been rendered limitless.

They are not. On that point, we prevailed completely. Indeed, the case has put us ahead of where we were before Obamacare. The Supreme Court has definitively ruled that the commerce, necessary and proper clause, and spending power have limits; that the mandate to purchase private health insurance, as well as the threat to withhold Medicaid funding unless states agree to expand their coverage, exceeded these limits; and the court will enforce these limits.

On the commerce clause, Chief Justice John G. Roberts Jr. and four dissenting justices accepted all of our side’s arguments about why the insurance mandate exceeded Congress’s power. “The individual mandate cannot be upheld as an exercise of Congress’s power under the Commerce Clause,” Roberts wrote. “That Clause authorizes Congress to regulate interstate commerce, not to order individuals to engage in it.”