The New Mexico Lottery Authority (NMLA) has voted unanimously to authorise a new sports lottery game.
However, the legality of the decision has been questioned by New Mexico State Representative Jason Harper.
The Santa Ana Star Casino & Hotel has already gone live with sports betting in New Mexico due to a compact with the state allowing tribes to offer sports wagers on sovereign land.
The NMLA, meanwhile, has approved a game where players have to correctly pick the outcome of at least three sporting events to win, which could debut in four to six months.
But Harper believes any such move would be "illegal" as overall sports betting has not been approved by state regulators.
He said: "My view is that, if the lottery moves forward with sports betting, that’s illegal.
"When the Supreme Court ruled, it did not change any laws in New Mexico. So why the lottery thinks it can do sports betting now again shows we have a rogue lottery in our state."