In 2012, the five conservative justices on the United States Supreme Court (including Chief justice John Roberts) held that key portions of the Affordable Care Act (ACA) exceeded Congress’s constitutional authority under the Commerce Clause. But, Chief Justice Roberts then joined the four liberal justices on the Court in upholding the ACA as a tax under Congress’s taxing power because it generated revenue for the federal government.

Fast forward five years: In 2017, the Republican-majority Congress did not have the votes to repeal the ACA but did set the individual mandate penalty at zero. In doing so, Congress eliminated the Court’s sole constitutional justification for upholding the ACA — a tax of zero is not a tax.

Texas and nineteen other states recently sued challenging the current constitutionality of the ACA. Individuals subject to the ACA mandates, represented by the Texas Public Policy Foundation, also joined this lawsuit. The parties argue that because the ACA individual mandate penalty no longer generates revenue, it is no longer a tax; therefore, Chief Justice Robert’s justification upholding the law no longer applies, leaving the ACA now unconstitutional — just like the five conservative justices have already opined.

It seems pretty straightforward.

A recent op-ed at The Federalist claims that striking down the ACA would be “judicial activism.” The article doesn’t defend the ACA as constitutional, but argues that conservatives shouldn’t ask “unelected judges to do what elected members of Congress took great pains to avoid.”

Such a broad view of “judicial activism” would render virtually any judicial review out of bounds. More importantly, it is contrary to the very system of checks and balances set up by the Founders in the Constitution. There is no Constitutional duty to persuade a majority of Congress to stop violating the Constitution—that’s what makes it a written constitution in the first place.

James Madison said the courts are designed to be an “impenetrable bulwark” against majority usurpations of constitutional rights. As early as 1795, the Supreme Court explained:

“If a legislative act oppugns a constitutional principle, the former must give way, and be rejected on the score of repugnance…in such case, it will be the duty of the Court to adhere to the Constitution, and to declare the act null and void…. the Judiciary in this country is not a subordinate, but coordinate, branch of the government.”

The opinion in that case was drafted by Justice William Patterson. Patterson was a delegate to the Constitutional Convention and part of the Congress that passed the Judiciary Act, which created the federal court system.

Instead of striking down the ACA, the author in The Federalist argues for a broad view of the severability doctrine. Under that doctrine when a law doesn’t have a severability provision, the court will ask whether Congress “would have” passed the law if the unconstitutional portions had not been included. If so, the Court will carve out the unconstitutional portions of the law leaving the remainder in effect.

But as Justice Clarence Thomas noted just this month, that is judicial activism at its finest. The canons of statutory construction say that courts must assume every word in a statute is meaningful. The realities of lawmaking make it likely that every word of a law like the ACA was the result of some compromise to secure votes so that the law would pass. Severing the unconstitutional language from the ACA and allowing the rest to stand wouldn’t be deferring to the decisions of Congress, it would be the Court effectively rewriting the law.

And there is the rub. Judicial activism, rightly understood, is when a court tries to exercise the legislative function — i.e., when a court writes laws instead of saying what the law is. But asking courts to carve out the unconstitutional provisions from laws is exactly that. Advocating for severability asks the judicial branch to judge the law Congress should have written, not the one it did. A more restrained approach would be to strike down the whole law and let Congress decide whether it wants to pass the law again without the unconstitutional provisions included.

An old saying goes something like: “When you mix a cup of sewage in a barrel of wine, you end up with a barrel of sewage and have to throw the whole thing out.” To extend the metaphor, courts shouldn’t be in the business of sifting through a law to pick the sewage out of the wine, they should throw the whole thing out. Striking down unconstitutional laws is not judicial activism, and it is well within the role of the judiciary to strike the entire ACA as such.