Cheaper than building a fence and provides a long term solution.

Nearly every city code requires that dogs are on a leash when not on the owners private property.

Buy a camera and point it at your lawn.

Every time the dog comes in your yard or even on the public street without a leash call the pound/city animal control.

Each city is different but with video evidence they will follow the procedures in the city code. The city will start fining the owner for every violation and remove the dog if necessary. My neighbor has gone from a boxer to a poodle and now has a miniature taco bell dog that never leaves the house.