The Illinois Service Member Employment and Reemployment Rights Act (ISERRA) requires an employer to reinstate and reemploy returning employees under the same terms and conditions as required by the Uniformed Services Employment and Reemployment Rights Act (USERRA). Time off under ISERRA is generally unpaid.
Effective immediately, however, Illinois has introduced an additional benefit under ISERRA. A service member whose employment is interrupted by a period of active service must be permitted, upon request of that service member, to use during such period of service any available unused, accrued vacation, annual, or similar leave with pay. An employer may not require any such service member to use vacation, annual, or similar leave during such period of active service. This applies to both paid and unpaid active service, including, but not limited to: travel to and from military orders, rest periods immediately before or after military orders, and military service during which the service member does not receive pay from the military.
You can access the enacted bill here.