WASHINGTON - A Government Accountability Office study quietly released Thursday has bolstered a Republican senator’s efforts to force Amtrak's rail service to accommodate gun toting riders or face shutdown, Raw Story has found.

The GAO ruled Thursday that an amendment inserted into a transportation funding bill by Republican Sen. Roger Wicker (R-MS) was permanent law, erasing doubts that Amtrak would have to comply. The mandate would force Amtrak to reverse a longstanding rule banning passengers from bringing guns onto trains instituted after 9/11.

The ruling comes just one week before the cash-strapped rail service must report back to the U.S. Senate with a plan to provide for gun-owning passengers. Wicker's amendment would strip the passenger rail service of $1.6 billion in federal funding if it does not formulate a gun-friendly plan.

If Amtrak doesn't come up with a way to allow guns, the law would effectively shutter service to congested areas like the so-called Northeast corridor between Washington DC and New York.

“In our eyes this is a victory,� said Ryan Anniston, spokesman for the Mississippi senator who inserted the amendment into the $68.8 billion Senate transportation and housing and urban development spending bill in early 2010. “We expect Amtrak will comply.�

The Amtrak law is what is considered an "unfunded mandate," a law passed by Congress that requires compliance to a government agency or government-subsidized program but doesn't provide additional resources.

In recent testimony before the Senate, Amtrak's security chief warned that the company was already short on money to adequately address terrorist threats. Amtrak is a favorite fiscal target of prominent Republicans like Sen. John McCain (R-AZ), who killed funding for a high speed rail service in 2008.

“As Amtrak has more than 500 stations, we are always resource-constrained,� Amtrak Police Chief John O’Connor testified in April.

In his testimony, Amtrak's top security officer said that one of the most likely scenarios for an attack on a train is terrorists bearing firearms.

“While terrorists can employ many tactics, overwhelming historical evidence indicates that terrorist attacks on surface transportation will likely occur in (3) forms:  Use of improvised explosive devices on a trains, use of an IED at a station, [or an] emerging threat as an active shooter,� O'Connor said.

“We will continue to devote the bulk of our efforts to defending against and deterring the most likely and dangerous forms of attack, which will continue to be IEDs and active shooters,� he added.

Making matters worse for the fiscally challenged rail service is the lack of additional funding to implement a gun-stowing plan, which would require special screening for passengers who wish to store guns on board.

“There is no pot of money that comes with this bill,� said Amtrak spokesman Steve Kulm.  “But we will find the money somewhere and we are on schedule to deliver a plan.�

Kulm said he didn't know how much the program will cost Amtrak.

Amtrak’s Chief Financial Officer recently told Congress that the rail service has an ongoing $5 billion backlog of capital projects that do not have funding.

Still, despite threats to close it, Amtrak the rail service remains popular. In 2009, the railroad carried 27.2 million passengers, the second-best year in the company’s history.

Sen. Wicker, who received an “A� rating from the National Rifle Association, has been adamant in arguing that the second amendment should apply to Amtrak passengers.

“Americans should not have their Second Amendment rights restricted for any reason, particularly if they choose to travel on America's federally subsidized rail line,� Wicker said at the time the amendment was passed, according to the National Rifle Association web site.

“Sportsmen who would like to use an Amtrak train for hunting trips cannot do so because they are not allowed to bring a firearm in checked luggage, something that is done every day at airports across our country,� he added.

Wicker's Amtrak gun amendment passed by a wide margin in September 2009, with 68 senators voting in favor and 30 against.