Yes, they are obligated because decisions must always be based on legal authority which typically are statutes, regulations, and/or previous court opinions. And decisions must follow logical precedent set by previous cases. This process is called Stare Decisis.
No, the Illinois court is not obligated to follow the Iowa Supreme Court’s decision, because each case is different and each court may have different precedents and different ways to control it.
If the United State Supreme Court had decided a similar case, yes that decision would be binding in the Illinois court. Because the United States Supreme Court is the highest court in the United States, and it has appellate jurisdiction over some courts and original jurisdiction over some cases.
1) A federal statute conflicts with the U.S. Constitution.
The U.S. Constitution will take precedence over a federal statute because it is the “supreme law of the law.” Any law in violation of the Constitution will be declared unconstitutional and will...