Invasive Bamboo

A customer's neighbour has some fantastic bamboo growing next to the neighbouring fence.

Unfortunately, it's rhizomes have crept underneath and the shoots are somewhat spectacular. They punch through a thick membrane without even producing any bumps. Within a couple of weeks, the 6ft + green canes are a sight to behold.

The customer had approached the neighbour about the issue but he couldn't care less.

My question is - how would you go about resolving the issue? A deep barrier, maybe? This would cost a wad of cash

If weedkiller was administered 'intravenously' on the soft shoot tips growing where they shouldn't be, and the parent growth suffers as a consequence, what would the potential fallout (legally speaking) be?

 

The barrier doesn't have to be deep. I remember Chris Beardshaw said that bamboo roots do not go deep into the soil, and he specified a depth; unfortunately, I've forgotten his measurement. But I have some invasive bamboo before. I followed the roots and all were eradicated. Neighbours are dreadful things.. worse than the bamboos. One fortunate thing is that they don't go deep, quite unlike some tenacious acanthus.