At first I thought "The canon-law tag should be attached to every question which can be validly asked a canon law student in a examen (or for research)." and I added tags to many questions.
Now I thought a bit about this and think the situation is more complicated. There are questions that can answered both out of a canon-law point of view and a theological/dogmatic point of view. These answers may differ, so I think the OP should clarify which answers he wants.
Take an example. In the question What is seen to actually occur if a female were to be the subject of laying on of the hands in ordination? there are two answers. One cites a theological Letter of Pope John Paul II. One cites the CIC. Both come to same answer. This will occur often as the head of the magisterium of the church is the Pope who also gives the laws of the chruch. So canon law is the practical side of the teaching of the church. But to this question a third answer could be added using the theological point of view. Not all Catholic theologicans agree with the Pope in that teaching and there is again a debate, if the cited letter is states a dogma and is infallible. And if one comes to the conclusion that it is no dogma and the canon law could be altered, there is the question wether women ordinations before that really were invalid (as canon law says) or only illicit (canon law is not infallible).
So we see there can be different answers to a question if you just take the canon law for granted or if question it critically from a dogmatic point of view. So OP should say what he wants.
I think the best solution is to use the canon-law tag when a question is about the nature of canon law (1) or explicitly asks about an answer out of canon law perspective (2). The tag should not be used if only Catholic views (3) or explicitly theological answers are requested. In case 3 answering with canon law is fine too (Should Catholic answers cite canon law?), but may not be the best way to answer the question. In cases 1 and 2 answers not using canon law do not fit to the question.