Yn ei brif ddyfarniad ef,  mae’r Arglwydd Hope yn penderfynu fel a ganlyn: “Acts of the Scottish Parliament are not subject to judicial review at common law on the grounds of irrationality, unreasonableness or arbitrariness” .  Ond os yw deddfwrfa ddatganoledig yn mynd yn groes i reolaeth y gyfraith (e.e. diddymu adolygiad barnwrol neu leihau rôl y llysoedd wrth amddiffyn buddiannau unigolion) mae’r Arglwydd Hope o’r farn y byddai’n bosibl dal bod Deddf gan y ddeddfwrfa honno yn anghyfreithlon. Ein safiad erioed ar ran Cymru oedd cytuno os felly yr oedd hi, ni fyddai dim gwahaniaeth rhwng Deddfau’r Cynulliad a Deddfau Senedd y DU yn y cyswllt hwn.  Felly nid ar y pwynt hwn yr oeddem yn ceisio amddiffyn y setliad datganoli.
In his leading judgment, Lord Hope decides that “Acts of the Scottish Parliament are not subject to judicial review at common law on the grounds of irrationality, unreasonableness or arbitrariness” .  His Lordship leaves open the possibility that an Act of a devolved legislature that contravenes the rule of law (e.g. abolishing judicial review or diminishing the role of the courts in protecting the interests of individuals) might be held to be unlawful .  However, our position on behalf of Wales was always to agree that if this was the case, then the Acts of the Assembly would be in no different position in this respect than Acts of Parliament, so that this was not the issue upon which we sought to protect the devolution settlement.