A word of advice to the Blagojeviches: whatever you do, don't get a divorce.

An Illinois law dating to the 1960s may help protect the state's foul-mouthed first lady as the federal government proceeds with its investigation and prosecution of her husband, Gov. Rod Blagojevich.

Illinois penal code bars Patricia Blagojevich from testifying against her husband about "any conversation [held] between them during marriage," a result of a "marital privilege" law that keeps the content of their contact private, just as conversations between a priest and penitent are off the books.

"Mrs. Blagojevich cannot be compelled to testify against the governor without his consent," said Judge Andrew Napolitano, senior legal analyst for FOX News. "So very little purpose could be used in squeezing her" -- pressing charges against her in an attempt to get to her husband.

U.S. attorneys charged Gov. Blagojevich with corruption Tuesday. FBI agents arrested him at his home in Chicago for allegedly trying to sell President-elect Barack Obama's vacant U.S. Senate seat. Federal courts would honor the Illinois state law on spousal privilege if they bring a case to trial.

Phone taps captured the governor "conspiring to sell the Senate seat in exchange for" -- among other things -- "his wife's placement on paid corporate boards," where she would receive at least $150,000 a year, according to the criminal complaint filed by U.S. attorneys.

Patricia Blagojevich was mentioned 19 times in the federal file. And though she may not want to squawk, she's already said more than a mouthful.

On Nov. 10, the complaint alleges, Patricia Blagojevich participated in a two-hour conference call with her husband and others as they discussed ways to profit from appointing Obama's replacement in the U.S. Senate, and the means of hiding evidence of a "pay-for-play" scheme.

Click here to see the federal complaint.

The first lady also allegedly got on the phone on Nov. 3 as her husband spoke with someone identified as "Deputy Governor A," and suggested pressuring the owners of the Chicago Tribune to "just fire" the authors of an editorial that had criticized the governor.

As the Tribune Company prepared to declare bankruptcy and sought assistance in selling major assets like Wrigley Field and the Chicago Cubs, the first lady was overheard on the call telling her husband to "hold up that f---ing Cubs s---. ... F--- them," according to the complaint.

U.S. Attorney Patrick Fitzgerald refused to comment on other possible players in the alleged scheme. "I'm not going to comment on anyone not charged," he said. But federal officials have suggested that Patricia Blagojevich and others involved in the taped phone calls would be looked at as part of a continuing investigation.

Despite Illinois protections, defense attorneys say, the first lady may not be in the clear if she becomes a target of the federal investigation herself as one of those "conspiring" in the sale.

Marital privilege "means she's insulated from testifying against her husband, but that doesn't mean they won't go after her ... if she was aiding and abetting anything he was doing," said Mickey Sherman, a criminal defense attorney in New York.

"The best thing she's got going for her is the prosecution may not want to appear mean-spirited by focusing on the governor's wife," he said. "Why go after the mother of two kids when you're really after the governor?"

As the U.S. attorneys continue their investigation of the alleged pay-for-play scheme, the closer Mrs. Blagojevich stays to the lightning Rod, the safer both of them may be: spousal privilege is revoked if the marriage is ended.

Tune into FOX News' hour-long special on the Blagojevich scandal "Pay to Play: The Chicago Way," hosted by Greta Van Susteren, Saturday and Sunday at 9 p.m. EST.