http://www.ssa.gov/history/court.html'The constitutional basis of the Social Security Act was uncertain. The basic problem is that under the "reserve clause" of the Constitution (the 10th Amendment) powers not specifically granted to the federal government are reserved for the States or the people. When the federal government seeks to expand its influence in new areas it must find some basis in the Constitution to justify its action. Obviously, the Constitution did not specifically mention the operation of a social insurance system as a power granted to the federal government! The Committee on Economic Security (CES) struggled with this and was unsure whether to claim the commerce clause or the broad power to levy taxes and expend funds to "provide for the general welfare," as the basis for the programs in the Act. Ultimately, the CES opted for the taxing power as the basis for the new program, and the Congress agreed, but how the courts would see this choice was very much an open question. . .
It is too late today for the argument to be heard with tolerance that in a crisis so extreme the use of the moneys of the nation to relieve the unemployed and their dependents is a use for any purpose
than the promotion of the general welfare."'
IMO, you may ignore last 4+ paragraphs of the following.
http://www.lewrockwell.com/orig3/attarian7.html