Can cayenne pepper damage my lawn ?
No, it won’t hurt the lawn, but there is a bigger issue here. If the neighbor is physically bringing the dog onto your lawn, it is not the dog’s fault and putting cayenne pepper will cause great discomfort to the dog who has no choice. The dog, being unable to leave, will end up ingesting the pepper trying to clean his paws and getting very sick. Don’t take it out on the dog. You need to have a conversation with the jerk neighbor. If the conversation doesn’t work, a flaming bag of feces on the doorstep can be employed. Or you can report him for trespass. Personally, I like the flaming bag of poo.