What did the court decide in Jack Spring, Inc. v. Little?
Answered for: Illinois
We find the reasoning in Javins persuasive and we hold that included in the contracts, both oral and written, governing the tenancies of the defendants in the multiple unit dwellings occupied by them, is an implied warranty of habitability which is fulfilled by substantial compliance with the pertinent provisions of the Chicago building code.
Illinois' Supreme Court adopted the implied warranty of habitability and allowed its breach to be raised in a forcible entry and detainer action.
This answer is true in Illinois and nowhere else on this site. Another jurisdiction is another answer, or an honest gap: see what has been read for Illinois.