Legal theory and politics. Private social contracts and the constution.
Private social contracts (that may result in employment), can be considered an individual power and a private property right, that is guaranteed by the Ninth Amendment; in our Bill of Rights. From this perspective, the federal government has no enumerated authority to deny or disparage the private property right of individuals to create or dissolve private social contracts; including, those that may result in employment or discharge of an individual.
Article 1, Section 10 of the federal constitution; specifically denies the power to impair in the the obligation of contracts, to the governments of the several states. From this perspective, the several states have no US constitutional authority to impair, otherwise lawful private social contracts between private individuals, even if it results in an employment contract, or its dissolution.
From the point of view of the Ninth and Tenth Amendments, at-will forms of employment can be considered a private property right between individuals, and a state's right to protect that form of contractual obligation.
Article 1, Section 8 of the constitution, specifically authorizes our federal congress to provide for the general Welfare of the United States. From this perspective, providing for the general welfare, could be accomplished by correcting for market inefficiencies that are conducive to forms of poverty that are related to frictional unemployment. At-will unemployment compensation could help provide for the general Welfare by improving the efficiency of the labor market; thus, improving the general Welfare of all market participants in the US market for labor.