H.R. 5894 — RESTRAIN Act

This section replaces the conditional prohibition on U.S. underground nuclear weapons testing after September 30, 1996 (lifted if a foreign state conducts a test after that date) with an absolute prohibition on explosive testing of a nuclear weapon or any other nuclear explosion by the United States. The section further (1) prohibits use of funds authorized for FY2026 or any fiscal year to conduct such testing or explosions and (2) clarifies that the prohibition does not limit subcritical nuclear tests (i.e., tests of fissile materials not capable of sustaining an explosive nuclear chain reaction).