New Jersey has been trying to legalize sports betting for years. One of the primary hurdles for that legalization has been the federal Professional and Amateur Sports Protection Act (PASPA). That law, enacted by Congress in 1992, make it unlawful for a government entity to authorize, operate, etc., gambling on competitive games in which athletes participate. PASPA – also known as the Bradley Act – excluded Oregon, Delaware, Montana, and Nevada from its sports betting prohibitions. New Jersey (and any other state which had licensed casino gambling) had a 1-year window to pass laws permitting sports betting. However, New Jersey did not pass such a law within that window of time.
Later, in 2011, New Jersey voters approved an amendment to the state constitution to permit the legislature to create laws to permit sports gambling. (Sports gambling would still not be permitted for college sporting events taking place in the State of New Jersey or involving a New Jersey team.)
In 2012 the first Sports Wagering Act was introduced to permit betting on sports at racetracks and casinos. That Act was challenged by virtually all major sports associations (NFL, MLB, NHL, etc.) and ultimately struck down by the District Court as violating PASPA.