This chapter shall not be deemed to provide a basis for any action, either legal or equitable, by any person or class of persons challenging a Federal project, program, or other activity that may affect farmland: Provided, That the Governor of an affected State where a State policy or program exists to protect farmland may bring an action in the Federal district court of the district where a Federal program is proposed to enforce the requirements of section 4202 of this title and regulations issued pursuant thereto