DOVER, Del. - The Delaware Supreme Court has ruled that a law allowing sports betting does not conflict with the state constitution, paving the way for Delaware to become the only state east of the Rocky Mountains to allow wagering on the outcome of games.

In a 22-page ruling dated Wednesday, the court said the state constitution permits lotteries that have an element of skill, as long as chance is the predominant factor in winning or losing.

The opinion came in response to Gov. Jack Markell's request for the court's views on a law he signed earlier this month authorizing a sports-betting lottery.

"I am very pleased with the Supreme Court's decision," read a statement by Markell, who is relying on the lottery to help overcome a projected revenue shortfall of more than $600 million for the coming fiscal year.

The ruling could lead to a legal challenge by professional sports leagues, which contend that sports betting would tarnish the image of athletics and lure young people into gambling.

Kenneth Nachbar, an attorney who represented the NFL in oral arguments before the Supreme Court last week, did not immediately return a telephone call seeking comment.

As envisioned by Markell, the sports lottery would allow straight bets on the outcome of athletic events, using a point spread or money line to ensure roughly equal amounts of wagers on each side; over-under betting on the total score of a game; and parlay bets in which players must select two or more elements, such as the winner of two or more games or two or more over-under bets.

Participants would not be allowed to wager on games involving college, amateur or Delaware-based professional teams.

The state is seeking proposals from potential vendors to oversee the lottery and working on the rules and regulations. Officials hope to have sports betting in place for the start of this year's NFL regular season in September.

Because of a brief, failed experiment with a sports lottery in the 1970s, Delaware is one of only four states grandfathered under a 1992 federal law that bans sports gambling. The other states are Nevada, Montana, and Oregon.

A key issue addressed by the justices was whether lotteries under the state constitution must be games of pure chance, or predominantly chance. While the state constitution does not define the term lottery, the court turned to previous rulings for guidance.

The justices noted that in a 1977 ruling in the NFL's challenge of Delaware's first sports lottery, a federal judge concluded that lotteries need not be matters of pure chance, and that "an element of calculation or even of certainty" could be involved, as long as chance was the dominant or controlling factor.

Lawrence Ashby, an attorney directed by the court to argue against the legality of sports betting, contended last week that skill was an essential element of sports betting because oddsmakers continually revise betting lines to take into account changing circumstances and to attract more gamblers.

The justices also said that the proposed sports lottery satisfied the constitutional requirement that lotteries be under state control, even though the state would hire a licensed bookmaker who might not be a state employee.