A more thorough explanation:

virtute cujus

virtute cujus is a Latin phrase that means "by virtue whereof." It was commonly used in legal pleadings to justify an entry onto land by claiming that it was done by order of someone who had the right to give such an order.

Example 1: The farmer claimed that he had the right to enter the neighboring field virtute cujus, because the owner of the field had given him permission to do so.

Example 2: The construction company argued that they had the right to build on the disputed land virtute cujus, because they had obtained a permit from the local government.

These examples illustrate how virtute cujus was used in legal contexts to justify actions taken on someone else's property. It was a way of saying that the action was authorized by someone who had the right to give such authorization.