Patriot Inventory Protection Act This bill requires the Army to evaluate its ability to meet war fighter requirements and operational needs, if GEM-T interceptors are removed from its operational inventory, by either: (1) recertifying GEM-T interceptors; or (2) developing, testing, and fielding a new low-cost interceptor that can be placed on the Army's operational inventory prior to the retirement of GEM-T interceptors. GEM-T interceptors are surface-to-air Patriot Guided Enhanced Missiles. The bill prohibits funds made available for the Army for FY2018 or thereafter from being obligated or expended to demilitarize any GEM-T interceptor or to remove any such interceptor from its operational inventory until the Army submits such evaluation to the congressional defense committees. Such limitation shall not apply to activities that the Army determines are critical to the safety of GEM-T interceptors.