The right to legally enter a property and take something from it is best referred to as:

The concept of having the right to legally enter a property and take something from it is accurately described by the term "Profit a prendre." This legal right allows an individual to enter another person’s land to harvest natural resources, such as minerals, timber, or game. Essentially, it grants the holder a specific entitlement to benefit from what the land produces, reflecting an agreement or law that recognizes this privilege.

Adverse possession, while related to rights over property, involves the process of acquiring ownership of land through continuous and unauthorized occupation, not specifically the right to take resources from another's land. Encroachment refers to intruding on someone else's property, typically by building a structure on it, which does not convey the legal right to take resources. Lastly, the exercise of Crown rights pertains to the government's rights over land, which is a different consideration entirely and does not deal with individual rights to enter a property for resource extraction. Thus, "Profit a prendre" is the most fitting term for the described situation.