House Republican Leader (and soon-to-be Speaker of the House) John Boehner late yesterday filed his brief as amicus curiae in support of the plaintiffs' motion for summary judgment in Florida v. HHS. The brief is (as all the amicus filings in this case will be), well, brief. (The page limit is 15.) The gist of his argument is that the minimum coverage provision exceeds Congress's enumerated powers, and that the United States's "interpretation of the Necessary and Proper Clause would create incentives for Congress to pass ill-conceived or unrealistic statutes." He does not address the commandeering question presented by the ACA's Medicaid amendments.
You can find Representative Boehner's brief here.