People responsible for making decisions on that person's behalf would have to be sure that those decisions are in that person's best interest and that there is no other way to look after them safely.
Byddai'n rhaid i bobl sy'n gyfrifol am wneud penderfyniadau ar ran y person hwnnw fod yn sicr bod y penderfyniadau hynny er budd pennaf y person hwnnw ac nad oes ffordd arall o ofalu amdano’n ddiogel.