Understand the concept of excludability: An excludable good is one where it is possible to prevent people who have not paid for it from having access to it.
Analyze each option: Consider whether it is possible to exclude non-payers from using each good.
The court system: Generally, access to the court system is not restricted based on payment, so it is non-excludable.
Public roads: These are typically available for use by everyone, making them non-excludable, although toll roads can be an exception.
National Defense: This is a classic example of a non-excludable good because it protects all citizens regardless of individual payment.