LANSING -- The U.S. Supreme Court decided Monday not to get involved in a dispute over how to prevent invasive Asian carp from making their way into the Great Lakes.

The justices turned down a new request from Michigan to consider ordering closure of Chicago-area shipping locks to prevent the fish from threatening the Great Lakes. The locks could provide a pathway to Lake Michigan for the unwanted carp.

The court had previously declined twice to order the locks closed on an emergency basis while it considered whether to hear the case. This time, the court rejected a proposal by Michigan and six other states to use a long-standing case involving water diversion from Lake Michigan as a vehicle for seeking to permanently sever a man-made linkage between the Great Lakes and the Mississippi River basin.

Michigan has led the legal fight to close the locks, arguing that the ravenous carp, weighing up to 100 pounds, could decimate the lakes' $7 billion fishing industry by starving out competitors such as salmon and walleye.

Mike Cox, the state's attorney general and a Republican candidate for governor, said responsibility for blocking the carp's advance now lies with President Barack Obama and Democratic congressional leaders. The Obama administration sided with Illinois in opposing closure of the locks.

"While President Obama has turned a blind eye to the millions of Great Lakes residents who do not happen to live in his home state of Illinois, it is now up to him to save thousands of Michigan jobs and our environment," Cox said.

The justices gave no explanation for their decision. The two-sentence order denied both Michigan's request to reopen the diversion case or, as a fallback, let the state file a lawsuit raising the same issues.

Although the high court refused to accept a new lawsuit, Michigan could file one in federal district court, said Nick Schroeck, executive director of the Great Lakes Environmental Law Center in Detroit. But doing so would take months, and "meanwhile, the carp are knocking at the door," he said.

Bighead and silver carp were among Asian varieties brought to the southern United States in the early 1970s. Government officials and private aquaculturists thought the newcomers could gobble up unwanted algae at sewage treatment plants and fish farms.

But the carp escaped into the Mississippi and have been migrating northward ever since. They have infested sections of the Illinois River and have reached an electronic barrier in the Chicago Sanitary and Ship Canal, about 25 miles from Lake Michigan.

A team of biologists says it has detected DNA from the carp past the barrier — and even within Lake Michigan itself. But no actual carp have been found between the barrier and the lake, despite an intensive search.

The sanitary and ship canal was built a century ago as engineers reversed the flow of the Chicago River to send water from Lake Michigan southward toward the Mississippi. It created an artificial linkup between the Great Lakes and Mississippi watersheds that has provided a pathway for invasive species.