As anti-American protests erupt in the Muslim world, the United States is powerless to act against those who incited the violence due to the freedoms enshrined in its cherished constitution.
The catalyst for the conflagration, which spread across the Middle East and North Africa on Thursday, was an amateur film denigrating Islam that was made and promoted by evangelical and Coptic Christians living in the United States.
"The US government is powerless in the specific sense that the constitution allows Americans to speak this way without fear of being thrown in prison because some people find what they say blasphemous," professor Eugene Volokh, an expert on free speech law, told AFP.
The suspected producer of the film is Nakoula Basseley Nakoula, a 55-year-old Coptic Christian living in California. It was promoted on the websites of two other Americans, extremist Christian pastor Terry Jones and another Copt, Washington-based Morris Sadek.
While Nakoula enjoys police protection at his home in the Los Angeles suburbs, the FBI is probing the deaths of four American nationals, including the country's envoy to Libya, killed during protests over the film.
The circumstances surrounding the storming of the Benghazi consulate on Tuesday are murky and US authorities believe Al-Qaeda-linked extremists may have planned the attack under the cover of the protests.
But the demonstrations that started hours earlier in Cairo and have now spread to much of the Middle East and North Africa are largely over the film, a trailer of which was dubbed into Arabic and promoted on the Internet.
The Justice Department refused to be drawn on what avenues it may be pursuing to punish Nakoula and others, but experts said there was nothing they could do to restrict people from exercising their constitutional rights.
The First Amendment to the US constitution states that: "Congress shall make no law... abridging the freedom of speech."
For 50 years, the key Supreme Court precedent was the 1919 Schenck v. United States ruling, which allowed for exceptions in cases of "clear and present danger."
This was superseded in 1969 by Brandenburg v Ohio, in which the judges held that the government cannot punish inflammatory speech unless that speech is directed to inciting, and likely to incite, "imminent lawless action."
The so-called Brandenburg test -- of intent, imminence, and likelihood -- holds sway today, and explains why the US government is powerless to punish the filmmakers or prevent a repeat of such an episode.
At a campaign event in Colorado on Thursday, US President Barack Obama said "no act of terror" will "dim the light of the values that we proudly present to the rest of the world."
"Innocence of Muslims," an amateurish production with bad dubbing and false beards and a cast that thought it was working on something entirely different, has caused easy harm and placed fresh scrutiny on those values.
Volokh, who teaches free speech law at the University of California, Los Angeles (UCLA), said, like it or not, the First Amendment protects the freedom of speech for everyone, crass and high-minded alike.
"That's true with Salman Rushdie, that's true with the producers of South Park. That's true with these people," he told AFP.
"Even advocacy of violence is protected and this isn't advocacy of violence, this is just parody of and criticism of religion."
The premise, Volokh explained: "If you give thugs the power to suppress speech by essentially saying that once your speech angers thugs you have to stop speaking, the consequence will just be more thuggery."
In the Internet age, any meaningful change of law would essentially call for a total ban on any speech that might incite fanatical Muslims to react with murder.
There has been speculation that Nakoula could face some charge at least for breaking his parole for earlier financial crimes charges, but Volokh thought this unlikely.
"I can't imagine that there was a patrol restriction when he was convicted for fraud that said 'and while you're on parole you can't make any blasphemous movies.'"
Steve Klein, an evangelical Christian who admits to being a consultant on the movie, said he was not responsible for the deaths.
"In this case with the ambassador, I did not kill these people. It is they who pulled the trigger. It is they who murdered the ambassador," he told CNN.