Call the police every single time one of them comes on your property. Every time. Call the non-emergency number, explain there is a neighbor trespassing on your property, and you'd like them removed. Don't lie, don't make up shit about weapons, just tell the truth. Hopefully the first time the message will be received by the neighbors. Depending on how frequent this occurs, officers will become aware of it. If the same officer keeps responding, they'll more than likely notify their Sgt or district commander about the ongoing issue. IANAL but I am a career 911 dispatcher, and while everyone has their own opinion on police, they are also humans who get annoyed at having to do the same shit over and over, and they will become less and less polite with your neighbors.

Also, depending on your local laws, it could be criminal trespassing. In my jurisdiction an officer officially warns you the first time, and if the same person is found trespassing on that property again within 12 months they are actually arrested, jailed overnight, and see a judge in the morning just like a thief or drunk driver (pre-covid, now it's just a signed promise to appear, and if they don't appear, warrant time)

Good luck!