according to this USA Today article:

WASHINGTON — The alleged crime at the heart of a controversy that has consumed official Washington — the "outing" of a CIA officer — may not have been a crime at all under federal law, little-noticed details in a book by the agent's husband suggest.

In The Politics of Truth, former ambassador Joseph Wilson writes that he and his future wife both returned from overseas assignments in June 1997. Neither spouse, a reading of the book indicates, was again stationed overseas. They appear to have remained in Washington, D.C., where they married and became parents of twins. (Related story: Bush waits on Rove)

Six years later, in July 2003, the name of the CIA officer — Valerie Plame — was revealed by columnist Robert Novak.

The column's date is important because the law against unmasking the identities of U.S. spies says a "covert agent" must have been on an overseas assignment "within the last five years." The assignment also must be long-term, not a short trip or temporary post, two experts on the law say. Wilson's book makes numerous references to the couple's life in Washington over the six years up to July 2003.

"Unless she was really stationed abroad sometime after their marriage," she wasn't a covert agent protected by the law, says Bruce Sanford, an attorney who helped write the 1982 act that protects covert agents' identities.

The leaking of Valerie Plame's identity started a chain of events that now has the White House at the center of a political firestorm as some Democrats demand President Bush fire close aide Karl Rove. Rove discussed Plame's CIA connection with Time reporter Matthew Cooper in 2003, though without naming her, according to Rove's attorney.

Joseph Wilson would not say whether his wife was stationed overseas again after 1997, and he said she would not speak to a reporter. But, he said, "the CIA obviously believes there was reason to believe a crime had been committed" because it referred the case to the Justice Department.

Spokesmen for both the CIA and federal prosecutor Patrick Fitzgerald, who is investigating whether a crime was committed, also would not comment.

Though that key law may not have been broken in leaking the name, Fitzgerald must still be pursuing evidence of some type of wrongdoing, said Victoria Toensing, another of the attorneys who helped draft the 1982 act. Like Sanford, she doubts Valerie Wilson, as she now refers to herself, qualified as a "covert agent" under that law. She and Sanford also doubt Fitzgerald has enough evidence to prosecute anyone under the Espionage Act. That law makes it a crime to divulge "information relating to the national defense" that "the possessor has reason to believe could be used to the injury" of the nation.

But, Toensing said, "reading between the lines, I'd say he's got a 'Martha Stewart case' " involving perjury or obstruction of justice. In other words, though a crime may not have been committed at the start, one may have occurred during the investigation when someone lied to Fitzgerald or to a federal grand jury.