I am not sure that the person asking this question has done much research (which may be a different reason to close it) but there are a variety of ways to answer it that don't get into "truth" wars or debates. I provided a link to a related question, and we have a variety of questions about saints ... is this question actually a dupe of something else?
The question seems to be:
What gives the Catholic Church and some Orthodox Churches and Anglican Union the right to declare saints?
The "truth question" label for this question isn't my favorite, but I think it can be defended by looking at the structure of the question:
What gives Group A the right to do Action X?
Note that the question does not ask whose view is desired. So Group A could answer "God," while Group B could answer "Nothing," and Group C could answer "Satan." That is, this question is more similar to:
Does Group A have the right to do Action X?
According to Group A, what gives them the right to do Action X?
But despite all that, even if the question were reframed to explicitly ask the "according to..." part, I'm still inclined to consider the question too broad. I don't get any sense from the question itself that the Catholic Church, "some" (only some?) Orthodox Churches, and the Anglican Union are going to have reasonably convergent answers on this question. Is there unity among the Anglican Union on this? How about within the mysterious "some" among Orthodox Churches?
Maybe I'm wrong, and there really is only one answer to it (once we more carefully define the groups we are talking about), but the question would be much stronger if it actually gave some basis for that implicit assumption. That would simultaneously give some reassurance to close voters that the scope for answers is suitable for this format.