"It is unfathomable that the administration is considering something so short-sighted and dangerous, and that directly contradicts its own 2018 Nuclear Posture Review (NPR). The NPR, which this administration often cites as inviolable, makes clear that ‘the United States will not resume nuclear explosive testing unless necessary to ensure the safety and effectiveness of the US nuclear arsenal'", the lawmakers said in their letter to Esper.
The letter demanded an explanation of the legal authority to resume testing, as well as a detailed account of how the test would be funded. Because Congress controls the budget, lawmakers have the option of cutting off funding for programs that lawmakers find objectionable.
The letter to Esper was signed by House Armed Services Committee Chair Adam Smith and Appropriations Committee Chair Nita Lowey, as well as chairs of three subcommittees with oversight over US nuclear weapons.