The latest issue of The Economist has a good article about allowing American states to set their own migration policies.
Last spring, Cato published a policy analysis on this very topic by Brandon Fuller and Sean Rust, entitled “State-Based Visas: A Federalist Approach to Reforming U.S. Immigration Policy.” Cato’s policy analysis explores the legalities, economics, and practical hurdles of implementing a state-based visa system in addition to the existing federal system. Cato even had an event in March 2014 (video available) where critic Reihan Salam and supporter Shikha Dalmia explored the idea.
The Economist article lays out the case well. Canada and Australia have state- and provincial-based visa systems that complement their federal immigration policies. The results have been positive for those local jurisdictions because they have more information and incentive to produce a better visa policy than a distant federal government does. American states could similarly experiment with less restrictive migration policies, attracting workers of any or all skill types.
The economic impact of immigration is positive, so the downsides of decentralized immigration policy would be small. Most importantly, The Economist echoes a point that Fuller and Rust made in their policy analysis: these migrant workers should eventually be able to move around the country for work. An unrestricted internal labor market is positive for the American economy; a freer international labor market would be too.