Either it did or it didn't.
You surely know that the courts do not issue advisory opinions. The court cannot act until a case is brought before it. The point is that President Lincoln had plenty of leeway to -act-. It was -then- for the courts to decide the validity of that act.
Walt
The courts DID decide the validity of that act in Ex Parte Merryman. Lincoln failed to appeal that decision as was his burden to do if he did not like it.