Yes of course in seriousness it shouldn't really need a law except in a massive case where perhaps civil law would suffice anyway. After all, if after many attempts at amicable resolution, polite complaints, proof of costs incurred by damage or work required to clean up etc etc, I would have thought someone minded to sue in civil court, could probably do so with a good lawyer and a good read of the law books. As you say, a simple and sociable approach of keeping it yourself is the best approach, and I wouldn't want my neighbours disliking me for such things either so I would probably be more inclined to clear them for that reason than for my own sake in all honesty! We did have some when I got here, and the previous owners had horses incredibly. We destroyed them all quickly and they haven't returned so far, thank god. we just have a forest of rush and thistles instead, but I am told Thistles are great for bees so thats something I suppose! Yin and yang etc.