The blessing of the AG is important. First, he is the chief law enforcement officer of the land. Second, and perhaps most important for this case, it means that DOJ has carefully reviewed the case law, precedent, and prior rulings by appellate courts and found that the emergency declaration is fully compliant with previous cases - the legal basis of any appellate court review.
It also signals that DOJ is very confident they can defend this declaration in the real courts - not the court of CNN or MSNBC.
All true. We have had 58 national emergencies declared since 1979.