I think it'll boil down to how much threat there was to his safety or the safety of others. By the strict letter of the law he might be right but since there was no evidence at all that they posed any danger to him then he may have a hard time avoiding jail.
Anything past the “property line” is felony trespassing and every private property owner has the constitutional right to protect that private property. This slow encroachment onto and into private property is communist ideology.