Federal Extreme Risk Protection Order Act of 2018 This bill amends the federal criminal code to authorize and establish procedures for a family or household member, or law enforcement officer, to request an extreme risk protection order with respect to an individual who poses an imminent risk to themselves or others. An extreme risk protection order is a federal court order that prohibits a person from owning, possessing, receiving, or having control or custody of a firearm. The bill also expands the categories of prohibited persons (i.e., persons barred from receiving or possessing a firearm or ammunition) to add a new category for persons who are subject to a court order that prohibits them from purchasing, possessing, or receiving a firearm.