My question involves real estate located in the State of: California

My house backs up to a neighbor's backyard and we have a lattice fence at the end of my small deck for some privacy. The edge of the deck and lattice are about 6" within my property. The lattice has a small area cut into it that allows my cat to come and go. We had an oral agreement for the past 7 years with the owner of the property that my cat was allowed to enter her backyard.

The original owner of the house has moved out and I don't know if she has sold or is renting the house. The house currently appears empty. Today I find that someone has sloppy nailed boards to my lattice and has blocked the hole for my cat to access.

What are my rights in this situation?