Final answer:
The Illinois court is not obligated to follow the decision of the Iowa Supreme Court on a new issue. However, if the US Supreme Court had decided a similar case, its decision would be binding on the Illinois court.
Step-by-step explanation:
When a county court in Illinois is deciding a case involving an issue that has never been addressed before in that state's courts, it is not obligated to follow the decision of the Iowa Supreme Court on a similar issue. The principle of binding authority states that a court must follow a higher court's decision in the same jurisdiction, but this only applies to decisions from the same state or federal jurisdiction. Therefore, the Illinois court is not bound by the Iowa Supreme Court's decision. Similarly, if the United States Supreme Court had decided a similar case, its decision would be binding on all lower courts in the country, including the Illinois court.