It is not an issue that can be tested in court. Even if the Mutual Legal Assistance Treaty (MLAT) had any such provisions for legal redress, Nigeria appears not ready to toe the path.

To end the impasse created by the United States (U.S.) government's rejection of the Federal Government's request for assistance to prosecute senior officials linked with the $180 million Halliburton scam, the country's legal team is turning to the American Congress for assistance.

Similarly, criticisms trailing the government's approach to the issue are also believed to have informed the advice of the lawyers hired by Nigeria to liaise with the U.S. authorities to look beyond the Justice Department for help.

The Guardian learnt that lawyers have written a letter to the Attorney-General and Minister of Justice, Michael Aondoakaa (SAN), advising him to reach out to the American Congress believed to be sympathetic to the Nigerian cause.

The lawyers, Kayode Oladele, a Nigerian based in the U.S. and Jack Blum, former United nations (UN) asset recovery expert, are also on their own meeting members of the U.S. Congress to prevail on the Executive arm to have a rethink.

Last week, the U.S. Justice Department rejected Nigeria's request for Mutual Legal Assistance over the $180 million Halliburton matter.

The lawyers said they would continue to pressure the American government on the matter, and called for more political and diplomatic steps from the Federal Government.

According to the legal team, the American House of Representatives is already aware of the case and but the lawyers want the Federal Government to also contact the Senate and specifically request both Houses to wade into the matter.

Previous mention or reference to the issue in the country's House of Representatives last month was at a broad and general level as the House Financial Services Committee at a public hearing sought ways to improve on U.S. government support for international anti-corruption efforts.

The House conducted the hearing on the theme: "Capital loss, corruption and the role of Western financial institutions." It heard the Nigerian saga among other international cases.

Now that the U.S. government has refused to release the list, Oladele said in his legal opinion to the Attorney-General, which The Guardian obtained, the Federal Government cannot sue the U.S. government on the violation of the MLAT.

His words: "The Treaty provides for withholding of execution of MLAT request by the central authority of the requested state for reasons enumerated by the United States under Article 111(3).

"That provision in the MLA therefore, makes a recourse by Nigeria to American courts seeking judicial intervention infeasible.

"As a way forward, the Nigerian government should make a strong representation to the United States Congress through both the House Financial Services Committee and the Senate Foreign Relations Committee with a view to expressing a deep disappointment and concern over the U.S. position and soliciting the Congress's support for the immediate execution of the request."

Oladele said the House Financial Services Committee was fully aware of the matter and the problems associated with the execution of the request and may urge the government to reconsider its position by immediately turning the evidence over to Nigeria.

The lawyers also proposed a political and diplomatic angle, asking that Nigeria should make a representation "directly to the U.S. government through diplomatic channels."

On May 19, 2009, the Halliburton matter was mentioned at the U.S. House of Representatives.

At the public hearing, Blum warned that if the American government does not act on time, the recovery of the funds might become impossible.

Referring to his testimony before the U.S. House, Blum said in an interview that "the key defendant" in the Halliburton scandal had already pleaded guilty since September last year and in his "plea, reference is made to payments to three high Nigerian government officials between 1995 and 2002."

But he told the Congress Committee that the Nigerian officials said to have received the money remained unidentified and if the U.S. government does not act promptly, it might be difficult to unravel the crime.