A so-called statement of immunity signed by Blackwater bodyguards questioned by a State Department investigative team is standard boilerplate used to protect federal employees during official administrative inquiries, law enforcement officials said Tuesday.

The "immunity" statement, called a Garrity Clause, does not prevent the Blackwater guards from being prosecuted in a court of law for any charges relating to the Sept. 16 shooting in Nisoor Square in Baghdad that left 17 Iraqis dead.

But a former FBI counterterrorism official says the case being made by the FBI is tougher now because investigators cannot use the initial statements made by the Blackwater guards. The FBI was sent by the State Department two weeks after the incident to probe whether the guards shot indiscriminately.

"It doesn't preclude these individuals from being prosecuted. What it does is just make the FBI's investigation extremely difficult, which they're very good at going back and reconstructing these types of things. These statements that they used — the statements that they had given to the diplomatic security, they're not going to be able to use those in court," said Richard Schoeberl, a former FBI agent in the counterterrorism division.

A copy of the immunity statement, obtained by FOX News, reads:

"I understand that ... disciplinary action, including dismissal from the Department's Worldwide Personnel Protective Services contract, may be undertaken if I refuse to provide this statement or fail to do so fully and truthfully. I further understand that neither my statements nor any information or evidence gained by reason of my statements can be used against me in a criminal proceeding except that if I knowingly and willfully provide false statements or information, I may be criminally prosecuted for that."

State Department spokesman Sean McCormack insisted Tuesday that the Blackwater guards are not off the legal hook.

"The Department of State cannot immunize an individual from federal prosecution," he said.

The Justice Department also issued a statement Tuesday saying it can't discuss the details of the case, but the Blackwater guards are not clear from possible criminal charges.

"Any suggestion that the Blackwater employees in question have been given immunity from federal criminal prosecution is inaccurate. The Justice Department and the FBI continue the criminal investigation of this matter knowing that this investigation involves a number of complex issues. We are unable to comment further at this time," reads a written statement from Justice Department spokesman Dean Boyd.

The Garrity Clause does require the guards to agree that any information or evidence resulting from statements furnished "may be used in the course of disciplinary proceedings, which could result in disciplinary action, including dismissal."

"The kinds of, quote 'immunity' that I've seen reported in the press would not preclude a successful criminal prosecution," McCormack said.

Lawmakers are in no way pleased with what they are hearing. Rep. Henry Waxman, chairman of the House Oversight and Government Affairs Committee, had been conducting his own probe of the shootings until the Justice Department requested lawmakers wait until the FBI concludes its inquiry.

He wrote Secretary of State Condoleezza Rice on Tuesday asking for details of the decision-making behind the grant of immunity, and the deal, but said he wasn't yet looking for witness statements provided after the immunity was given.

"This rash grant of immunity was an egregious misjudgment. It raises serious questions about who conferred the immunity, who approved it at the State Department, and what their motives were," Waxman, D-Calif., wrote.

House Judiciary Committee Chairman John Conyers and Democratic Reps. David E. Price and Janice D. Schakowsky also sent a letter to Rice and Acting Attorney General Peter Keisler requesting more information about the immunity deal.

"It is our understanding that as a result of any immunity given to the guards, prosecutors will have to prove that any evidence they use in bringing criminal charges against the guards was uncovered independently of the guards' initial statements. This would apparently make the prosecution more difficult," the lawmakers wrote.

The company has defended itself against accusations by saying its convoy was under attack before it opened fire. A follow-up investigation by the Iraqi government, however, concluded that Blackwater's men were unprovoked. No witnesses have been found to contradict that finding.

An initial incident report by U.S. Central Command, which oversees military operations in Iraq, also indicated there was "no enemy activity involved" in the Sept. 16 incident. The report says Blackwater guards were traveling against the flow of traffic through a traffic circle when they "engaged five civilian vehicles with small arms fire" at a distance of 50 meters.

According to a source familiar with the investigation, 19 Blackwater employees are implicated in the shooting, as well as two Blackwater employees in a helicopter sent to the scene after trouble was reported. Two or three of the Blackwater employees have returned back to the U.S. because their contracts ended. A total of five of the 21 Blackwater employees reportedly opened fire with their weapons.

Those who have remained in Baghdad working for Blackwater are carrying out limited duties within the "wire" — or Green Zone. They have not been allowed to accompany diplomatic convoys since the Sept incident, the source said.

A Blackwater spokesman said the company is fully cooperating with the FBI investigation. A source close to Blackwater said the guards' initial statements under the Garrity Clause can be used in a court of law if any of the guards accused any of the other guards of wrongdoing.

The Garrity Clause protects the individual from making self-incriminating statements. It is not immunity granted by the State Department, but a guarantee protecting federal employees and automatically received as a result of several Supreme Court precedents, the source said. The State Department apparently believes the independent contractors are government actors for Garrity purposes.

Meanwhile, Rice and Defense Secretary Robert Gates met in the Pentagon for an hour Tuesday to discuss greater oversight of security contractors.

I believe it's safe to say all this stuff needs to be tightened up, that we need to be more clear about whether it be the standards by which (contractors) are trained, their understanding of (the) mission, their rules for use of force and clearly coordination," said Pentagon Press Secretary Geoff Morrell. "There has not been a satisfactory coordination of movement to this point.

On Tuesday, Iraq's cabinet drafted a bill for the parliament to lift the immunity of private contractors operating in Iraq. Blackwater's contract is up in May and Prime Minister Nouri al-Maliki doesn't want it renewed.

FOX News' Jennifer Griffin and The Associated Press contributed to this report.