Courts didn't "make up" the law.
Time to refute your sourceless falsehood again.
"As we have seen the basis of Common Law was custom. The itinerant justices set out by William the Conqueror examined the different local practises of dealing with disputes and crime, filtered our the less practical and reasonable ones, and ended up with a set of laws which were to be applied uniformly throughout the country."
who were these itinerant justices??? Why, judges of the court set forth by the Crown.
and what do you call the process these judges of the court were engaged in whereby they examined, filtered, the customs and practices as to ended up with laws to be applied??? Why, they were making up laws via this process.