By Thierry Lévêque and Alexandria Sage
PARIS, May 10 (Reuters) - Outgoing French President Nicolas Sarkozy, who has enjoyed legal immunity for the past five years, could soon be forced to explain himself to magistrates in three separate funding scandals that have dogged his time in power.
France's constitution says a president cannot be required to testify or be investigated or prosecuted until a month after leaving office, a privilege that will end in mid-June for Sarkozy, who hands over to election winner Francois Hollande on May 15.
That frees the way for Sarkozy to be summoned for questioning by judicial investigators looking into murky affairs including a 1990s submarine sale to Pakistan and relations between Sarkozy, his party and France's wealthiest woman.
"It's written, black on white, that proceedings begin at the expiration of a time limit of one month after the end of his functions," said Matthieu Bonduelle, president of France's magistrates' union.
Sarkozy has denied involvement in any of the cases, which have already sparked judicial investigations and embroiled some of his wealthy friends.
The allegations of scandal also clouded Sarkozy's campaign for the 2012 presidential race, which he lost last Sunday to Hollande.
One scandal involves Liliane Bettencourt, billionaire heiress of the L'Oreal cosmetics empire. Investigators want to know if cash withdrawals from her Swiss bank accounts were used to illicitly fund Sarkozy's 2007 presidential campaign.
Bettencourt's former wealth manager, Patrice de Maistre, is in custody and expected to be questioned by a judge on Thursday over Swiss cash withdrawals of as much as 800,000 euros in the months prior to Sarkozy's victory.
De Maistre will likely also be asked about ties to the treasurer of Sarkozy's UMP party at the time, former Labour Minister Eric Woerth, who, like de Maistre, is formally under investigation.
In the second case, the so-called "Karachi Affair", judges are trying to unravel a series of nebulous dealings by middlemen and possible kickbacks linked to the sale of Agosta class submarines by the French government to Pakistan in the 1990s.
Sarkozy, who was budget minister and spokesman for presidential candidate Edouard Balladur at the time, has angrily rejected media speculation that he might have known of the payments. Judges want to know if they made their way to the Balladur campaign.
"I can't tell you whether, in each of these cases, there are enough elements to place Mr. Sarkozy under investigation," said Bonduelle, who is not involved with any of them.
"These are enormous cases and we only know a few pieces of information that are in the press," he added.
The most recent headache for Sarkozy was the publication last month by investigative news website Mediapart of a document it said showed that deposed Libyan leader Muammar Gaddafi's government had sought to fund Sarkozy's 2007 election campaign.
Sarkozy sued Mediapart, calling the document an "obvious fake" and a judicial investigation has been opened to ascertain the veracity of the document that Libya's National Transitional Council has called a fake.
Sarkozy's predecessor, Jacques Chirac, who ruled France from 1995 to 2007, was handed a two-year suspended jail sentence in December after a court found him guilty of misusing public funds for political purposes when he was mayor of Paris.
Chirac was questioned within two months of leaving the presidential palace.
President-elect Hollande has pledged to change the rules so that a president, starting with himself, can be questioned while in office on judicial matters that pre-date the presidential mandate. (Reporting By Alexandria Sage; Editing by Robin Pomeroy)