Is there any pre-modern document (or was there any, if it didn't survive) in Welsh or Irish history, which is broadly equivalent in intention and purpose to the Declaration of Abroath or the Magna Carta?
Are there Welsh or Irish documents that assert national rights against authority, whether internal or external? For example, there could be the rights of Welsh lords against their king, or against an English king.
I'm not a historian. Apart from Google, I wouldn't know where to look.