The services listed in Annex III were established by binding Union acts, whilst other services operate on a voluntary basis.
Rinneadh na seirbhísí a liostaítear in Iarscríbhinn III a bhunú le gníomhartha ceangailteacha de chuid an Aontais, cé gur ar bhonn deonach a fheidhmíonn seirbhísí eile.