HomeNATO Status Lists ...27. Protocol to the North Atlantic Treaty on the Accession of the Republic of Bulgaria, done at Brussels March 26, 2003 hide 27. Protocol to the North Atlantic Treaty on the Accession of the Republic of Bulgaria, done at Brussels March 26, 2003 Depositary – Treaty Affairs Office of Treaty Affairs Entered into force February 27, 2004. Enters into force when each of the parties to the North Atlantic Treaty has notified the Government of the United States of America of its acceptance of the Protocol. Download Status List [34 KB] Tags Multilateral North Atlantic Treaty Organization Treaties