110 ILCS 985/2

The minor children of persons who, having resided in this State for at least 12 months immediately prior to such a transfer, are transferred by their employers to some location outside the United States shall be considered as Illinois residents for purposes of the computation and payment of tuition at any State supported school. However, this Section shall apply only when the minor children of such parents enroll in a State supported college or university within 5 years from the time their parents are transferred to some location outside the United States.