I can see why it might look that way, but that isn't how it actually works out. As the owner he can refuse you entry; as long as you aren't on his land, he can't touch you. If you attempt to force entry, he can indeed defend himself.
Supposing you are on his property because you were allowed on, he can't defend his property against your "trespassing", because you aren't trespassing. What you're suggesting is that the land owner might now say, "I want you off my land in one second... ONE! OK, now you're a trespasser!" and start shooting. He cannot do that because in allowing you onto his land, he made an implied contract that he would not molest you, including assault or imprisonment. He volunarily waived his right to call you a trespasser when he invited you onto his land.
He can of course order you off his land, but the contract implicit in his originally allowing you in, means that he must give you sufficient time to get off his land. If you're standing right at the property line, he might legitimately give you the count of three before he starts shooting, but if you're deep in his land somewhere, he must allow you to depart.
...then he can’t just ban “anything he wants” on his property.
He can, but only with advance notice. For example, he might invite you onto his land on the condition that you sign a waiver, acknowledging that the landowner will shoot you if he feels like it. You'd be a fool to sign the contract, but if you signed it and entered his land, he'd then be within his rights to shoot you. If, on the other hand, he invites you to dinner and up and kills you, he's a murderer: his invitation implied a contract not to harm you during your visit. That isn't a limitation on his property rights; it's a case of a voluntary contract waiving certain rights.
Can he ban anything at all and if so what circumstances justify doing so?
He can make absolutely any rules he wants, but he can't then change the rules at a whim. This answers your original objection, but leaves open the possibility that he might lawfully organize a "paintball" game using live ammo.
The law doesn't work that way today, however. Courts do not respect the liberty of contract, so for example a contract to provide assisted suicide, or sexual services, would be nullified by the courts. But I think it was already clear to you that we're discussing "shoulds", not current US law.
"What you're suggesting is that the land owner might now..."
No I am not suggesting that. I'm saying that the words “…he can ban anything he wants on his property, including his parking lot. Forcing him to do otherwise is a violation of his rights” suggest that.
"...he made an implied contract..."
As a property owner I might quote (with minor changes): "My observation is that the supposed "implied contract" is not in fact a contract. For starters, nobody signed it, least of all me--so this is a contract that binds me against my will."
And also: "You're claiming I'm a party to a contract that I never agreed to, that you can't even state with any certain detail, that provides no clear enumeration of responsibilities nor specific provision of penalties for breach... in other words, a "implied contract" is nothing like a "contract"."
Can he [the landowner] ban anything at all and if so what circumstances justify doing so?
Izzy answers, making up his own 'law':
He can, but only with advance notice.
For example, he might invite you onto his land on the condition that you sign a waiver, acknowledging that the landowner will shoot you if he feels like it.
You'd be a fool to sign the contract, but if you signed it and entered his land, he'd then be within his rights to shoot you.
If, on the other hand, he invites you to dinner and up and kills you, he's a murderer: his invitation implied a contract not to harm you during your visit.
That isn't a limitation on his property rights; it's a case of a voluntary contract waiving certain rights.
He can make absolutely any rules he wants, but he can't then change the rules at a whim. This answers your original objection, but leaves open the possibility that he might lawfully organize a "paintball" game using live ammo.
The law doesn't work that way today, however.
Courts do not respect the liberty of contract, so for example a contract to provide assisted suicide, or sexual services, would be nullified by the courts. But I think it was already clear to you that we're discussing "shoulds", not current US law.
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Kris, what we have here is 'bold' evidence of a very naive mind. -- Izzy and I started out discussing the 'implied social contract' aspects of the US Constitution. [a very libertarian document, to my mind]
Now izzy wants to claim that all along he has been arguing utopian libertarian theory. --- [IE -- "you {can} ]sign a waiver, acknowledging that the landowner will shoot you if he feels like it."]
Bizarre stuff.
Rational libertarians agree that our US Constitution is a valid social contract based on the free will of everyone who resides in this country. Any individual is free to renounce citizenship and/or leave to avoid honoring our Constitution & its valid laws.
But it is implicit, -- that if you stay here, you play by Constitutional rules. -- [you do not ban guns in your parking lot]