Here’s the relevant UCI rule on safe sprinting:
Riders shall be strictly forbidden to deviate from the lane they selected when launching into the sprint and, in so doing, endangering others.
Also there’s a general rule on conduct:
1.2.079 Conduct of participants in cycling races
All licence holders… …shall refrain from any acts of violence, threats or insults or any other improper behaviour or from putting other persons in danger.
Renshaw seems to have fallen foul of the more general rule. The decision is controversial and it can be argued that Julian Dean was potentially putting Mark Renshaw into danger by trying to force him aside. But this was a subtle move, the repeated series of head-butting was asking for trouble and it’s something that’s going to be on TV news bulletins around the world this evening.
I’m wondering aloud if Renshaw is being used as an example pour encourager les autres. His ejection from the race sends a powerful signal that the riders can’t resort to violence or even aggressive positioning. What frustrates is the lack of consistency, riders can do something one day and they race on; the next time they’re packing their suitcase.
Certainly the rules need to be clearer, a specific mention forbidding the use of the head, fists etc in the UCI rulebook would help clear things up.