Common sense is sufficient for most things. The problem with law is that what gets to court are the weird edge cases that aren't covered by common sense.
Often by the time something reaches the court, there is no possible outcome that provides justice for all, and the court instead has to determine which of the parties to screw the least.
Often by the time something reaches the court, there is no possible outcome that provides justice for all, and the court instead has to determine which of the parties to screw the least.