The Commission, upon application or on its own motion, may by order or rule exempt for the future any class of agreements between persons subject to this chapter or any specified activity of those persons from any requirement of this chapter if it finds that the exemption will not result in substantial reduction in competition or be detrimental to commerce. The Commission may attach conditions to any exemption and may, by order, revoke any exemption. No order or rule of exemption or revocation of exemption may be issued unless opportunity for hearing has been afforded interested persons and departments and agencies of the United States.