Paragraph 887 of the CCC mentions episcopal conferences. From this same page, you can put this paragraph in context by reading the surrounding section of the Catechism.
http://www.ziplink.net/cgi-bin/cgiwrap/kerygma/a.pl?k=%22Episcopal+Conferences%22&b=C&t=and
Apostolic Letter on the Theological and Juridical Nature of Episcopal Conferences, issued motu proprio by John Paul II, 1998.
http://www.cin.org/jp2/apost.html