A national securities exchange may limit (A) the number of members of the exchange and (B) the number of members and designated representatives of members permitted to effect transactions on the floor of the exchange without the services of another person acting as broker:
Provided, however, That no national securities exchange shall have the authority to decrease the number of memberships in such exchange, or the number of members and designated representatives of members permitted to effect transactions on the floor of such exchange without the services of another person acting as broker, below such number in effect on
May 1, 1975, or the date such exchange was registered with the Commission, whichever is later:
And provided further, That the Commission, in accordance with the provisions of
section 78s(c) of this title, may amend the rules of any national securities exchange to increase (but not to decrease) or to remove any limitation on the number of memberships in such exchange or the number of members or designated representatives of members permitted to effect transactions on the floor of the exchange without the services of another person acting as broker, if the Commission finds that such limitation imposes a burden on competition not necessary or appropriate in furtherance of the purposes of this chapter.