Restatement black-letter rules had to state universally true propositions of law.

Evidence

The Institute early laid down for its draftsmen the requirement that every statement of law made in the black letter must be tiue in all … One notable exception was made at the insistence of the reporter, Professor Seavey, in the Restatement of Restitution, which was issued in 1937. — Henry M. Hart, Jr. and Albert M. Sacks, The Legal Process, 4371