You're welcome Eoin.
I'm not sure that a forum is the right place to ask the question if you are looking for a qualified reply to be honest.
In my experience, many aspects of our fishing rules and regulations are indeed subject to local variations under the management of associations, clubs, syndicates, councils and river beat proprietors. I can think of many examples, such as season start & finish dates, no fishing on Sundays, fishing allowed on Sundays, fly only rules, single hook fly only rules, barbless fly only rules, spinning rules for certain dates within the fishing season, spinning rules regarding water height, spinning rules regarding treble/single hooks on lures, bait fishing rules regarding specific dates within the fishing season, rules that say no bait fishing, rules that say bait fishing is only allowed for juniors, etc etc.
Best wishes
Mike