The subsidy payments to insurance companies may be “critical” to sustaining the ACA, but they are not provided for in the ACA. The Obamacare law did not appropriate them. No legislation appropriates them. They are and have always been illegal.To his credit, David Greene of NPR asked Zeke Emamuel about this very question of legality on "Morning Edition" and Emanuel's initial response was that Trump should have just kept on paying these unappropriated funds. Because Constitution-schmonstitution.
Extra - Red State: "Democrats Sue To Force President Trump To Break The Law And Ignore A Court Order." "The idea that a president can be sued with the objective of making him break the law is so outrageous that one wonders if “support and defend the Constitution of the United States” really has any meaning to the Democrat party."