Illinois is one of the 23 US states that allow the use of medical cannabis    . As of this writing, Illinois is one of the 23 US states that allow the use of medical cannabis for medicinal purposes. 2. After getting a 61-57 and 35-21 support from the House and the Senate, respectively, the Illinois medical cannabis bill was approved on April 17, 2013, and signed into law on August 1, 2013. 3. Illinois' medical cannabis law is known as The Compassionate Use of Medical ...