Plaid Cymru is, so far as I know, the only political party in Wales to have taken a position on the issue of a Welsh legal jurisdiction. (The Welsh Government has, but that’s a government not Labour Party matter.) Responding to the recent WGC/Constitution Unit report, Leanne Wood said such a jurisdiction was ‘essential’.
This is not policy-making off the cuff. In 2010, Plaid Cymru held an internal discussion about the establishment of a Welsh legal jurisdiction and the form it should take. As their ‘consultation paper’ from that exercise isn’t otherwise available, and given the developing debate about this issue, with Plaid’s permission I’ve uploaded the paper in PDF format. The English version is available here, and the Welsh one is here.