Baltimore, Chicago, Cincinnati and Columbus argued in a lawsuit [text, PDF] filed Thursday in the US District Court for the District of Maryland [official website] that President Donald Trump’s plan to undermine the Affordable Care Act (ACA) is a violation of the US Constitution.

Congressional Republicans attempted and failed to repeal the ACA several times last year. Shortly after, in a series of tweets [Twitter post] as well as public statements, Trump promised to “let ObamaCare fail and then come together and do a great healthcare plan.” Further, the Trump administration said [JURIST report] in June that it will not defend portions of the ACA following a challenge by 20 states led by Texas, which filed [JURIST report] a lawsuit in February alleging that the ACA is unconstitutional after the passing of the new tax plan.

Thursday’s complaint argues that Trump has violated the Constitution’s “take care” clause, which requires the president to “take care that the laws be faithfully executed,” as well as the Administrative Procedure Act [text].

“Having failed to persuade Congress to repeal the Affordable Care Act, President Trump and his Administration are waging a relentless campaign to sabotage and, ultimately, to nullify the law,” the complaint states.

The lawsuit lists a number of ways the cities’ 4.5 million residents have been prevented from obtaining health insurance through ACA’s exchanges by, the “the breadth and persistence of the Trump Administration’s efforts to undermine the ACA”, for example: “promoting insurance that does not comply with the ACA’s requirements; slashing funding for outreach strategies that have been proven to encourage individuals, and healthy individuals in particular, to sign up for coverage; misusing federal funds for advertising campaigns aimed at smearing the ACA and its exchanges, and spinning false narratives about the efficacy and success of the Act” among others.