One who deals with an agent without knowing or having reason to believe that the agent acts as such in the transaction, may set off against any claim of the principal arising out of the same, all claims which he might have set off against the agent before notice of the agency.
Cal. Civ. Code § 2336
Mutual Obligations of Principals and Third Persons
Enacted 1872.
Official source: California Legislative Information. Reproduced from public-domain California statutes; confirm against the official source for the current text. Not legal advice.