Cats spoiling my garden

I would appreciate any advice on how to stop cats fouling on my garden.

We have just spent £700 on a garden within the last couple of weeks and have also bought a Mega Sonic Repeller (£22) and yet the cats are still fouling on the garden, including on the expensive stone work.

Can someone answer my questions please.

If it was a dog, the owner is required by law to pick the foul up.

Would cat owners, please, follow their cats at night and pick up their foul mess?

Can the owners offer any advice on how to resolve this problem?

Patricia Atkinson