Under Mr. Trump’s new rule, however, such plans can last for 364 days and can be renewed for up to three years. That rule joins an earlier one that allowed businesses to join together to create “association health plans” that also evade the Affordable Care Act’s strictures. In effect, these rules are creating a cheap form of “junk” coverage that does not have to meet the higher standards of Obamacare. This sort of splintering of the insurance markets is not allowed under the Affordable Care Act as Congress drafted it.

The Trump administration’s goal is not only to weaken the Affordable Care Act but also to trick the public into thinking, as opponents of the law like to say, that Obamacare is “collapsing under its own weight.” Let’s be clear: If the Affordable Care Act collapses, it is because the president demolished it.

Never in modern American history has a president so transparently aimed to destroy a piece of major legislation. What makes Mr. Trump’s sabotage especially undemocratic is that Congress has repeatedly considered repealing the law — and repeatedly declined to do so. In addition, the Supreme Court has twice sustained the Affordable Care Act in the face of major legal challenges. Mr. Trump’s attempt to destroy the law any way he can is an unconstitutional usurpation of power.

That is also the message of a lawsuit — the first of its kind — filed this month in federal court in Maryland. Brought by several plaintiffs including the cities of Chicago, Cincinnati and Columbus, the lawsuit recounts the “relentless and unlawful campaign to sabotage and, ultimately, to nullify” the Affordable Care Act. Taken individually, some of the Trump administration’s actions may be defensible. Taken together, they amount to a derogation of his constitutional duties.

The lawsuit asks the court to strike down the administration’s new rules and to enjoin the president from further sabotage. To prevail, the plaintiffs may have to overcome some procedural hurdles, including questions about whether the courts have the authority or the institutional competence to prevent violations of Article II’s requirement that the president “take care that the laws be faithfully executed” — especially given the wide discretion that presidents traditionally have to implement the laws.

But if there is ever going to be a viable claim along these lines, this is it. After all, no court has ever held that the president has the power to consciously aim, in bad faith, to destroy Congress’ handiwork. Yet with his attacks on this law, that is precisely what Mr. Trump has been doing. No matter how you feel about Obamacare, we should all care about that.

Nicholas Bagley is a professor of law at the University of Michigan. Abbe R. Gluck is a professor of law at Yale.

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