National Harbor developer Milt Peterson stands at the site where he wants to locate a high-end casino in Prince George's County. (Photo by Astrid Riecken for The Washington Post)

A provision to accomplish that in a gambling bill introduced in the regular session was deemed “constitutionally impermissible” by the Attorney General’s Office, which said in an advisory opinion that a local vote could not bind a state decision.

The bill that will be introduced in the special session will get around that concern by using nonbinding “intent” language, according to people working on the bill.

Under current law, any major gambling expansion — including the addition of a new casino — requires a statewide vote as well as legislative approval.

The O’Malley-backed bill, according to those working on the legislation, will include language that makes clear it is the General Assembly’s intent that regulators issue a license for a Prince George’s casino only if a majority of county voters back it in a statewide referendum.

Though the language is not airtight, it seems unlikely to be defied by state regulators. Moreover, O’Malley aides note, local casinos must comply with local zoning laws. So an anti-casino vote in Prince George’s could embolden county officials to use their zoning powers to block a facility.

If a gambling bill passes during the special session, the Prince George’s provision could have a major impact on the fall referendum campaign, focusing efforts of the opposition on county voters far more intently than on voters statewide.