Let's say there is an accident and there is a law which says vehicles driving by an avenue has priority to pass, but there is another law which says vehicles driving by the right has priority to pass, what happens when 2 laws conflict each other?
The court decides - that’s how common law evolves. Once the court has decided, the law is now “settled”.
For a real example that happened to an acquaintance. He was driving and collided with an unattended horse. Motor vehicle law says “don’t collide with other peoples property”, livestock law says “keep your livestock under control”. The court decided that he lost.