A trial court and the court of appeal have held that property owners who allowed a neighbor to landscape, irrigate and install lighting on a driveway easement across their property, had inadvertently and unintentionally given up a permanent irrevocable license for those improvements. The courts couldn't grant the neighbor an easement for the landscaping improvements, because there was no dispute that the property owners had consented to the improvements. Both courts held that because the property owners had allowed the neighbor to expend a considerable amount of money and effort installing and maintaining the improvements and over a long period of time, six years, that an irrevocable license had been established.
In order to create an easement, whether for access, landscaping, or any other use, either the owner of the property must make a deed granting the easement, or the person claiming the easement must use the easement area for five years openly and adversely. Adversely means without the consent of the property owner. Therefore, property owners have felt protected against giving up rights regarding their land when they allowed a neighbor to use a portion of it. Consent was and is still a defense to any claim to an easement. So is posting a "right to pass by permission" sign, pursuant Civil Code §1008. But it won't protect you from an irrevocable license on your property.
A non-easement permission to make such use of another person's property is a license, and in most situations, such a license is revocable at any time.
Richardson v. Franc, a January 27, 2015 case from Novato, recognized that the property owners' consent prevented the neighbor from acquiring an easement, but nonetheless gave the neighbor the permanent irrevocable right to keep and maintain the landscaping, irrigation system and lighting the neighbor had installed and maintained on the property for six years, with the owners' knowledge.
If you want to protect against someone acquiring the right come onto or cross your property, or to use your property for some purpose, like landscaping, your consent will protect against the creation of an easement, but it won't protect you against the creation of an irrevocable license under this case. Our advice is to offer to allow the other person to continue their use of a portion of your property only if that other person agrees to sign a written agreement that you can cancel such permission and block the access or remove the improvements upon written notice.
If the person attempting to use your property and establish such an easement or irrevocable license will not relent and will not sign such an agreement, then you must sue them. Maybe you can get them to agree to neighborhood mediation or mediation with an attorney or retired judge, to work something out. You can't just let them continue. That's what the Franc's did, and now they're stuck with their neighbors' landscaping, irrigation and lighting forever.