It's only fiction, but is it legal?

The last time a US president and Nicholson Baker appeared in the same sentence, the subject was sex: In 1998, Kenneth Starr discovered that the world's most famous intern had given Bill Clinton a copy of Mr. Baker's erotic novel "Vox."

But this time around, the subject is violence: Baker's upcoming novel, "Checkpoint," is about two men in a Washington hotel room arguing about whether to assassinate President Bush.

A work of literary fiction, it carries Michael Moore's case against Mr. Bush to extremes that the partisan moviemaker has never dared approach. It may also be the most specifically articulated argument about killing a sitting US president ever published by a major commercial publisher.

"Checkpoint" reads like an attempt to exorcise anger at Bush's international policies, but in a phone interview from his home in Maine, the author says, "No, this is a book about the rage and sadness of war, and about the moral consequences of war, boiled down to a conversation between two people. I want readers to think things through. Sometimes a novel is the best way of making that happen."

Thousands of popular novels are published every year based on fictional or real-life crimes, but in the current atmosphere of heightened national security, Baker's dramatization of a fact-based argument about killing Bush could be seen as incendiary. But does that make it illegal?

Threatening a president's life is a violation of US law, and Secret Service agents will show up on the doorsteps of people who, even casually or in jest, make a statement about killing the nation's commander in chief.

But the US courts also protect free speech and the press. In a 1969 case, the US Supreme Court said speech that advocates violence or illegal action could not be suppressed "except where such advocacy is directed to inciting or producing imminent lawless action and is likely to incite or produce such action."

"You have a substantial right to create fiction no matter what the subject matter," says David Greene, executive director of the First Amendment Project, a nonprofit advocacy group. "But it's slightly complicated when you're talking about threats against the president. If this were an author who was less acclaimed, you'd find him at a minimum being checked out by law enforcement. This Justice Department is more likely to investigate something like this."

FBI and Justice Department spokesmen refused to comment on Baker's book or to indicate if officials were investigating it.

"Checkpoint" had been scheduled to appear Aug. 25, just days before the Republican National Convention in New York, but this week Alfred A. Knopf pushed the book's 60,000 first printing up to Aug. 10.

The 115-page novella is framed as the transcript of a conversation between fictional characters Jay and Ben at a hotel a few blocks away from the White House in May 2004. Jay claims that he wants a record of his motives for killing the president later that day "for the good of humankind."

The two men apparently haven't seen each other for several years. While Ben has been enjoying some success in life, Jay has lost his job, left his family, and grown obsessed with President Bush's actions in Iraq. He often sounds mentally unbalanced.

Through much of their conversation, Jay recounts real stories lifted from news reports about the horrors endured by Iraqi civilians in both accidental and deliberate military encounters. The book's title comes from a particularly gruesome tragedy in April 2003 when US soldiers at a checkpoint near Najaf opened fire on a family of 17 Shiites. Eleven of them in their 1974 Land Rover, including six children, were killed.

Jay's argument swings wildly from an insane rant to caustic political analysis. Though most of his weapons - Bush-seeking bullets and a giant uranium ball - are clearly delusional, his final plan is pedestrian and deadly. While largely agreeing with his friend's recitation of Bush's sins, Ben struggles to calm Jay and get him to abandon his illegal plot.

"There are really strict legal standards on what constitutes a threat, and certainly a fictional conversation between fictional characters - it's almost impossible to imagine that that could rise to the level of a legal threat against the president," says Larry Siems, director of the Freedom to Write Program and of international programs for the PEN American Center. "Characters in novels don't kill presidents."

But, he notes, "there have been encroachments recently on the terrain of creative freedom that are connected with people's fears and anxieties.

"We know the Secret Service has visited high school classrooms where students have produced art that has made reference to violence. The whole atmosphere has shifted enormously."

The Supreme Court has been very clear about the rights of authors to write whatever they want so long as they are not intentionally inciting imminent violence, according to ACLU president Nadine Strossen. She says, however, that under Section 215 of the Patriot Act, "Mr. Baker wouldn't know and he wouldn't be able to find out if he's under surveillance. And anybody the FBI asks about him would be forced to be under that veil of secrecy."

Baker, meanwhile, said, "I'm trying to let the book do its own talking as much as possible."