OTTAWA - Brian Mulroney doesn't want to thwart an investigation of his business links to arms dealer Karlheinz Schreiber -- but he does want to know more about the ground rules for the probe, says the lawyer for the former prime minister.

Guy Pratte insisted Tuesday that Mulroney's latest legal move is "not an attempt to delay or derail this inquiry."

On the contrary, he told Justice Jeffrey Oliphant, Mulroney wants to "facilitate and expedite" matters so he can put the inquiry behind him and get on with his life.

Nevertheless, said Pratte, it's crucial for all involved to ensure "the rules of the game are known before it starts so we can prepare adequately."

Oliphant has already rejected a contention that the only proper yardstick for measuring Mulroney's conduct is the cabinet ethics code that he himself introduced when he took office over two decades ago.

In a decision issued last month, the judge said he must cast a wider net and take account of the ethical provisions embodied in various federal statutes, including the Financial Administration Act, the Income Tax Act and even the Criminal Code.

Oliphant reiterated Tuesday that doesn't mean he intends to hold anyone criminally or civilly liable -- which he's precluded from doing under his mandate.

"I'm sensitive to that and will take great care to avoid doing it," he told Pratte. "I assure you of that."

Beyond that general principle, said Oliphant, it's difficult to lay down hard-and-fast rules because he doesn't know yet where the evidence will lead him.

Paul Vickery, a lawyer for the federal Justice Department, chided Pratte for trying to resurrect past arguments already rejected by the judge.

If Pratte doesn't like last month's ruling he has the right to challenge it in Federal Court, said Vickery. Pratte has so far made no move to do that, and indicated Tuesday he'd prefer not to because it could be seen as a "disruptive" move.

Richard Auger, one of Schreiber's legal team, maintained the ground rules are already clear and urged Oliphant to resist further tinkering.

"There's no need to clarify, change or edit one word or comma," said Auger.

Pratte wants the judge to "clarify" last month's ruling by issuing a more precise directive on how he intends to employ the various provisions of the cabinet ethics code and the relevant statutes.

He also wants a fuller explanation of how Oliphant intends to judge Mulroney's conduct after he stepped down as prime minister -- a key issue, since the legal and ethical standards for public office holders may differ from those applied to private citizens.

Oliphant said he'll deliver an oral ruling on the request Thursday in an effort to dispose of the matter before hearings get under way.

The first witnesses are scheduled to testify next Monday and Tuesday, although the bulk of the public hearings won't get under way until mid-April.

Oliphant was appointed last year by Prime Minister Stephen Harper to get to the bottom of the contentious affair after Mulroney and Schreiber gave different versions of events to a parliamentary committee.

Mulroney says he accepted $225,000 from Schreiber after stepping down as prime minister in 1993 to promote the building of German-designed light-armoured vehicles in Canada. He says he tried to line up support among foreign political leaders whose countries might buy the vehicles.

Schreiber says the deal was struck before Mulroney left office although the cash didn't change hands until later. He also claims the payments totalled $300,000 and that Mulroney was supposed to lobby the Canadian government, not foreign leaders.

Schreiber, who faces charges of tax evasion, bribery and fraud in Germany, has long fought extradition from Canada. He's being allowed to stay in the country long enough to participate in the inquiry.