This applies to
public hunting areas during
firearm deer seasons.
From the IL 2006-2007 hunt regs, page 31.
[align=left]• Blaze Orange Requirement – Ground Blinds on[/align][align=left]Public Hunting Areas. It is unlawful to use or occupy[/align][align=left]a ground blind during any firearm deer season[/align][align=left]on public land unless at least 400 square inches of[/align][align=left]solid vivid blaze orange material is securely[/align][align=left]attached to the uppermost portion of the blind and[/align][align=left]a substantial amount of orange is visible for 360[/align][align=left]degrees.[/align]