I don't think it's a ban as such, more like they are ineligible to qualify for Europe via the English system. Implies to me that UEFA see them as a Welsh club, and so should be using a Welsh qualifying spot rather than an English one. Means they won't be playing in Europe for some time as clubs playing outside the Welsh leagues are ineligible for the Welsh Cup, which is how Cardiff (and I think Wrexham and Swansea also) have qualified before.