20 ILCS 1805/3

Whenever all or a portion of the Illinois National Guard is called or ordered into the active military service of the United States by the President of the United States or the Congress of the United States it shall be the duty of the Governor as Commander-in-Chief to furnish such troops, and the Governor as Commander-in-Chief may, by his proclamation, organize the Illinois State Guard under the provisions of the Illinois State Guard Law.