The ten FIS rules of conduct are, in the settled case law of the OGH, the recognised standard of care in the relationship between skiers. They were developed by the International Ski Federation and have no direct statutory force, but function as a concretisation of the due care required under § 1295 ABGB. Anyone who breaches a FIS rule and thereby injures another skier will in most cases have acted negligently.
The rules that are central in collision cases are: Rule 1 (consideration, every skier must behave in a way that does not endanger or harm others), Rule 2 (control, adapt speed and manner of skiing to personal ability, terrain, snow, weather and traffic density), Rule 3 (choice of track, the skier coming from behind or above must choose a line that does not endanger the skier ahead; the skier ahead has priority), Rule 4 (overtaking with sufficient distance) and Rule 5 (entering, starting again and moving uphill, look uphill first and yield to all).
For slope accidents between skiers, Rule 3 is the most practically relevant: the skier coming from behind or above bears the responsibility for the choice of track. Anyone who runs into a skier ahead has regularly breached Rule 3. Exceptions exist where the skier ahead suddenly blocks the way or has themselves breached Rule 5 (entering the slope).