What is the point of judicial review if the Supreme Court doesn't have the power to enforce the law?

If the Supreme Court declares a law unconstitutional, does it even matter if the court doesn't actually have the power to enforce it? I'm having a test over this tomorrow in government and I'm very confused about this. In Marbury V. Madison the court stated that Marbury's rights had been violated but they weren't able to do anything about it. Andrew Jackson also said once that John Marshall made his decision, now let him enforce it. I'm not seeing what the point of judicial review is.