Since the late 20th century and the rise of Indian activism over sovereignty issues, as well as many tribes' establishment of casino gambling on reservations as a revenue source, the US Supreme Court has been repeatedly asked to address the IRA's constitutionality. The provision of the Act that is controversial is the one that allows the US government to acquire non-Indian land (by voluntary transfer) and convert it to Indian land ("take it into trust"). In so doing, the US government partially removes the land from the jurisdiction of the state, which makes certain activities, such as casino gambling, possible on the land for the first time. It also makes the land exempt from state property taxes and some other state taxes. Consequently, many people oppose implementation of this part of the Act and, typically represented by state or local governments, they sue to prevent it.