A group of state lawmakers has filed a suit it hopes will blow the planned SugarHouse casino out of the water.

The legislators say that more than half the proposed Fishtown casino is to be built on submerged Delaware River bottom owned by the state and that the city had no authority to give developers "riparian rights" to build there.

"Simply put, the city's action represents a direct assault on the authority of the General Assembly to control lands owned by the commonwealth in trust for the public," said Catherine Recker, the attorney representing the lawmakers.

"It's really a question of sovereignty," said state Rep. Michael O'Brien, whose district includes the proposed SugarHouse site.

O'Brien is one of seven lawmakers who sued, including state Sen. Vince Fumo, and state Reps. Bill Keller and John Taylor.

In November, city Commerce Director Stephanie Naidoff issued a license to SugarHouse allowing it to build over the river, citing an obscure 1907 law that permitted the city to license the construction or repair of wharves, piers, bulkheads, docks, slips and basins.

Any authority the city had in the 1907 law was revoked in the 1978 Dam Safety and Encroachments Act, the lawmakers say. They've asked the state Supreme Court to affirm the Legislature's control over the issue and to revoke SugarHouse's city-granted license.

SugarHouse spokesman Dan Fee said that the company's executives believe that the city's legal reasoning is sound and that developers will be ready to begin construction in a matter of weeks.

"The effect of this lawsuit would be to give others from outside the Philadelphia area enormous say in developing our waterfront," Fee said.

O'Brien said the right way for SugarHouse to get its riparian rights is through an act of the Legislature. He said he won't even introduce a bill until developers work out a "community-benefits agreement" with neighbors.

"Whether you want to put a hot-dog stand on the Delaware, or relocate the Vatican on the Delaware, there is a process," O'Brien said.

A key question is whether incoming mayor Michael Nutter will support Mayor Street's stance in granting the casino riparian rights.

Nutter said in a phone interview yesterday that he'd always thought authority over riparian rights rested with the Legislature, and was "concerned" when the city granted SugarHouse a license "based on a law that virtually no one seemed to know existed."

But Nutter stopped short of saying he would try to reverse course after he assumes office Jan. 7.

"Upon taking office I and other officials of the administration will take a careful look at all the issues surrounding the proposed casinos, including any pending lawsuits and appeals," Nutter said.