Which of the following defenses is NOT effective against trespass to land claims?

In the context of trespass to land claims, the effective defenses hinge on the nature of the defendant's conduct and the legal rights attributed to landowners. A mistake of fact regarding ownership is not a viable defense in trespass cases because the law typically holds that individuals are responsible for knowing the boundaries and ownership of land. Even if a trespasser genuinely believes they own the property or are allowed to enter, that belief does not negate the unlawful entry.

In contrast, lack of intent to enter the property can serve as a defense if it can be shown that the entry was accidental or unintentional. Similarly, a good faith belief in the right to enter may provide a defense if it can be substantiated that the person reasonably believed they had permission, especially in cases involving invitees or social guests. Permission from the property owner is a clear-cut defense, as it validates the entry, making it lawful.

Overall, the unique characteristic of trespass is that liability stems from entering another person's land without authorization, irrespective of the trespasser’s beliefs about ownership or intent—thus making a mistake regarding ownership ineffective as a defense.