User blog comment:Goku484/Is Broly Cannon?/@comment-4072803-20120331150610

Technically, none of the movies fit securely into the preexisting timeline. The ones that take place during the 10 Days in Anticipation for the Cell Games (Broly- The Legendary Super Saiyan, and Plan to Eradicate the Super Saiyans), seem to fit the most, but they do have some problems. Most of all is the fact that they start out in their base forms. While one could argue that they immediatley transformed INTO the Full Power Super Saiyan state, but the few scenes in the actual SHOW seem to contradicte this (were they are in the FPSSJ form).

So, in an odd conclusion, I suppose it's up to the viewer whether Broly is canon or not. The same thing could be said of Tarble, were he TECHNICALLY appears after Z, but apparently before Goku met Uub. They never tell us if he stayed on the planet, however.