I think most if not all dioceses in ACANZP would understand that they belong to ACANZP by common compact and thus could dissociate by local synodical decision (albeit with consequences re breaking fellowship with other bishops). This right to dissociate - as I understand it - is even clearer in Australia where dioceses do not have to abide by decisions of the General Synod.
In other jurisdictions such possibilities are not quite so clear. I imagine it is impossible for a diocese to even contemplate dissociation in the C of E. But in TEC (USA) there have been dissociations (de facto), court cases which suggest dissociation is not possible (de jure) unless the General Convention should so approve and a dogged belief by the Diocese of South Carolina that it, at least, can dissociate because of some peculiarities in South Carolina state law.
Well, put simply, that dogged belief has complete victory today according to this Stand Firm post.
LATER: The definitive word on the legal niceties in this victory and the nuances which might influence other cases belong - unexpectedly - to Anglican Curmudgeon.