which constitutional power of congress was used to establish the individual mandate under obamacare
Health insurance mandate The ACA mandate was challenged in federal courts by Republican state Attorneys General. On June 28, 2012, the U.S. Supreme Court upheld the provision as Constitutional.[42] Chief Justice John Roberts delivered the majority opinion in National Federation of Independent Business v. Sebelius, which upheld the Patient Protection and Affordable Care Act by a 5-4 vote. The Court ruled that although the "individual mandate" component of the act was not constitutional under the Commerce Clause, it was reasonably construed as a tax and was therefore valid under the Congressional authority to "lay and collect taxes."[43][44]
Necessary and Proper Clause According to the Articles of Confederation, "Each state retains its sovereignty, freedom, and independence, and every power, jurisdiction, and right, which is not by this Confederation expressly delegated" (emphasis added). Thus, the Continental Congress had no powers incidental to those which were "expressly delegated" by the Articles of Confederation.[2] By contrast, the Necessary and Proper Clause expressly confers incidental powers upon Congress, while no other clauses in the Constitution do so by themselves.[2]