Yes, you are correct. This is what Illinois states:
If you were an Illinois resident when the gambling winnings were earned, you must pay Illinois Income Tax on the gambling winnings. Additionally, you may not include the gambling winnings in the non-Illinois portion of Schedule CR, Credit for Tax Paid to Other States.
https://www2.illinois.gov/rev/questionsandanswers/pages/468.aspx
Yes, you are correct. This is what Illinois states:
If you were an Illinois resident when the gambling winnings were earned, you must pay Illinois Income Tax on the gambling winnings. Additionally, you may not include the gambling winnings in the non-Illinois portion of Schedule CR, Credit for Tax Paid to Other States.
https://www2.illinois.gov/rev/questionsandanswers/pages/468.aspx
You must pay tax in Illinois.
You CAN take a credit on the IL-1040, Sched CR
So has Illinois change their law to now allow you to claim a credit for taxes paid to another state on gambling winnings?
The instructions for Illinois Schedule CR specifically state that "gambling, sports wagering, and lottery winnings" from other states should be entered on Line 15, Column B.
il-1040-schedule-cr-instr.pdf (illinois.gov)
In 2015 the U.S. Supreme Court ruled that states may not tax income that is already subject to taxation by another state. It held that states must provide credits to individuals or business to avoid double taxation of the same income.
https://www.scotusblog.com/case-files/cases/comptroller-v-wynne/