Ambiguum pactum contra venditorem interpretandum est is a legal maxim in Latin. This maxim states that an ambiguous contract is interpreted against the vendor (the person who wrote the contract).
The following is an example of a case law referring to the maxim:
Ambiguous restrictions, like provisions in other written instruments, are construed most strongly against the person who creates them. An ambiguous sale contract is construed against the seller, ambiguum pactum contra venditorem interpretandum est. [Parrish v. Newbury, 279 S.W.2d 229 (Ky. 1955)].