I am not a lawyer, but I can provide some general information. Whether it is legal or not to install a kill switch on your motorcycle lights can depend on the jurisdiction you are in and the specific regulations that apply to motorcycles in that area.
In some jurisdictions, it may be illegal to modify the lighting system of a motorcycle, as it can affect safety and visibility on the road. Manufacturers design motorcycles to meet certain safety standards, and altering the lighting system could potentially compromise those standards.
To ensure compliance with the law, it is advisable to consult your local traffic regulations or reach out to local authorities, such as the Department of Motor Vehicles (DMV) or law enforcement, for accurate and up-to-date information regarding the legality of modifying the lighting system on your motorcycle.
Keep in mind that safety should always be a priority, and any modifications made to your motorcycle should not compromise your visibility or the safety of yourself and other road users.