The several district courts of the United States are vested with jurisdiction specifically to enforce, and to prevent and restrain any person from violating any plan or regulation made or issued under this chapter. The facts relating to any civil action authorized to be brought under this subsection shall be referred to the Attorney General for appropriate action: Provided, That nothing in this chapter shall be construed as requiring the Secretary to refer to the Attorney General violations of this chapter whenever the Secretary believes that the administration and enforcement of any such plan or regulation would be adequately served by administrative action under subsection (b) of this section or suitable written notice or warning to any person committing such violations.