Been thinking a bit on your problem. I think I might have come up with a viable solution.
Moan a bit to a couple of neighbors about the dogs. Then video the dogs at the garbage cans, documenting. Then use something like this, with paintballs, still taping.
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Not expensive, definitely not lethal, limited range, not loud. Then, when the neighbors complain about someone paintballing their pooches, possibly calling the law on it, you can then, very innocently, hand over the tape to the nice officers; and, depending on your mood, deny any knowledge that those were our neighbors' dogs. If the dog(s) keep coming around, a flast of those plastic BBs in the rear should move them on their way - I'd keep a shotgun very handy thos, just in case one decided you were being too unfriendly. Fun for shooting cans in the backyard too, or even in the house.
JOAT If it ain't broke, don't lend it.
- Red Green