Legality
Unlike brass knuckles, weighted knuckle gloves are legal in most areas, as they are generally considered “less-lethal weapons", due to their defensive nature. In some jurisdictions, including Australia, they may be restricted under more general "dangerous weapons" laws.
In the United States, weighted knuckle gloves are illegal in the states of Massachusetts and California. In New York, sap gloves are not specifically denominated as unlawful weapons by state law. However, they may be unlawful to possess with intent to use them unlawfully against another.
In the United Kingdom, weighted knuckle gloves are legal to buy, sell and own. However possession in a public place without a reasonable excuse or lawful authority is illegal.
Read more about this topic: Weighted-knuckle Glove