As the founding fathers of the united States of America made clear in the Declaration of Independence in 1776:
"Governments are instituted among Men, deriving their just powers from the consent of the governed, that whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or abolish it, and institute new Government."
The US continues to suffer economic difficulties stemming from the federal government's neglect to reform domestic and foreign spending. The citizens of the US suffer from blatant abuses of their civil rights from acts such as the NDAA, the Patriot Act, the TSA, the DHS, etc. Given that the state of IL cannot maintain a balanced budget, it is practically feasible for IL to withdraw from the union & re-secure their rights.