Do you have automatic sprinklers?
If so, hook them up to a motion sensor.
Granted, that won't help if they throw egss from the street, but it'll keep them from getting any closer, with no legal worries.
Too bad it's not like the old days when you could send them on their way with an assfull of rock salt from a 12 gauge.
BTW - the motion-triggered sprinklers also help if you've got a neighborhood cat using your landscaping as its personal litterbox (again - if a shotgun is not practical)

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