I can think of two cases in the novels that we know of wands breaking.
- When Hagrid was expelled
- When Ron's wand was broken by the
Hagrid's wand was broken by the order of the state, so we can't tell if this is not legal. What it seems would be illegal is him buying another one as Olivander both know that he was expelled and makes sure that the wand was destroyed (it was not of course). So it does seem that wand breaking can be a form of exile from performing magic.
Ron's wand was broken maliciously but not by a person (I'm not sure if the whomping willow is sentient or not). However, we can see by the reaction of people to this that it is not that serious a matter. Harry and Ron are at the time in a lot of trouble, and the broken wand was an afterthought. If there were special circumstances around wand breaking you would think that it would be noted at this point. AS it is, it is seen as an annoyance by Ron rather than any special loss. Like a laptop or phone breaking, rather than the loss of a pet for example.
So in the absence of any contradictory evidence, I would say there is nothing special about wands breaking or being broken.