Final answer:
The exception to boat registration laws is if the boat is small enough to be exempted, depending on state requirements. Safety regulations may still apply.
Step-by-step explanation:
The exception to the law that states you must register your boat is if your boat is small enough to be exempted from registration. The specific requirements for exemption vary by state, but generally, boats under a certain length or with a certain type of propulsion may be exempted. For example, in some states, boats less than 16 feet in length or non-motorized boats like canoes or kayaks may be exempted. However, it is important to note that even though a boat may be exempted from registration, certain safety regulations may still apply, such as carrying proper safety equipment or following navigation and boating rules.