They absolutely have opinions, often about how to interpret the law. This is why Supreme Court decisions always have the "dissenting opinion" document listing

They absolutely have opinions, often about how to interpret the law. This is why Supreme Court decisions always have the "dissenting opinion" document listing out why they think the majority decision was incorrect. Many laws are not so black and white that the decision is explicit. You have to handle weird chain of custody questions, whether evidence was seized lawfully, etc, etc.