Uninvited “visitors” are welcome to the extent that they bring more of value than they take in return. That includes their absolute recognition that what’s mine is mine - taking my undisputed ownership of my property is an offense that cannot be balanced by any return. If they can work and produce something of value - skilled farming, metalwork, guard duty, reaction force skills, they may well be welcome. Traders may be welcome if they are well-behaved and covered by one of my family members during negotiations. Eventually, even after SHTF, trade will become extremely important.
Otherwise, any dispute over whether “visitors” are permitted on my property will be very short. Key supplies for responding to guests who feel entitled to things that are not theirs: ammo, a shovel, and the ability to avoid discussing the outcome.