Not to mention that cannonicity has been given an order for a reason:
1) G- Canon (movies and statements of George Lucas. Can also include novels of Episode's 1-6).
2) T - Canon (This one is new. But its basically all the new TV series theyre making. So the new CW Animation comes here, and also the new live action series due to come out soon).
3) C- Canon (basically everything else that fits into canon).
Now if it were just a matter of canon or not, then there would be no order here.. No G's and C's.
But there obviously is an order for a reason. So everything in C- Canon can be considered canon as long as it does NOT DIRECTLY CONTRADICT Canon sources T or G. If it does then its not canon.
A good example of this is a story before ROTS stating Ki-Adi-Mundi was appointed to the Jedi Council without being given Mastership. But then ROTS (a G canon source) clearly stated Anakin was the first one to be appointed to the council without being given mastership in Jedi history.
Therfore that specific part of the Ki-Adi-Mundi story is no longer valid and no longer canon. (which does not necessarily mean the WHOLE story is no longer canon)