Sign up today for the CNBC Sport Newsletter The NFL is asking prediction market operators to keep specific event contracts that the league deems "objectionable bets" off of their platforms. In a letter obtained by CNBC, the league outlines examples of event contracts that could be easily manipulable by a single person, inherently objectionable, related to officiating and knowable in advance — and asks that operators refrain from offering such trades. The NFL declined to comment on which