When a state wants to use its Medicaid program in a way that does not fit the requirements of the Social Security Act, they will frequently turn to Section 1115 of the Act, which allows states to seek a waiver of limiting requirements.
Update on Medicaid Expansion via 1115 Waivers, State Policy Report #59 (June 2016)
Centers for Medicare and Medicaid Services (CMS) waiver page (state-by-state information on current and pending waivers)
The following documents provide detailed examination of the 1115 waiver:
1115 Waiver Regulations (December 2007)