Federal Extreme Risk Protection Order Act of 2021 This bill authorizes and establishes procedures for federal courts to issue extreme risk protection orders. An extreme risk protection order is a federal court order that prohibits a person from purchasing, possessing, or receiving a firearm or ammunition. A family or household member, or a law enforcement officer, may petition for an extreme risk protection order with respect to an individual who poses a risk to themselves or others. The bill also expands the categories of persons who are prohibited from purchasing, shipping, transporting, possessing, or receiving a firearm or ammunition. Specifically, it adds, as a new category, persons who are subject to an extreme risk protection order.