2010 California Code
Civil Code
Article 1. Voluntary Interference With Property

2078.  One who officiously, and without the consent of the real or
apparent owner of a thing, takes it into his possession for the
purpose of rendering a service about it, must complete such service,
and use ordinary care, diligence, and reasonable skill about the
same. He is not entitled to any compensation for his service or
expenses, except that he may deduct actual and necessary expenses
incurred by him about such service from any profits which his service
has caused the thing to acquire for its owner, and must account to
the owner for the residue.