Restrictions Based on Convictions: Yes.
Documentation or Licensing: Until January 1st 2024 there is no issues
Where to Purchase: Can be purchased from dealers, retailers, or online suppliers until January 1st 2024.
Official Government Source: Illinois General assembly
After the January 1st 2024 of this amendatory Act of the 103rd General Assembly, it is unlawful for any person within this State to knowingly manufacture, deliver, sell, import, or purchase or cause to be manufactured, delivered, sold, imported, or purchased by another, an armor plate, body armor, or military helmet.
Except as otherwise provided, as of January 1, 2024, it is unlawful for any person within the state to knowingly possess body armor. Some exceptions are expressed in the act which can be found here.