“Critics contend that Judge Hudson has unduly restricted Congress’s authority to regulate interstate commerce, the principal basis on which the government defends the law. Some also claim that he ignored the ‘necessary and proper’ clause of the Constitution, which allows Congress leeway to choose how to put in place national economic programs. Yet a closer reading shows that Judge Hudson’s analysis could prove irresistible to the Supreme Court and that there is a reasonable chance it will agree that the insurance mandate is invalid.”