Washington: Efforts by US authorities to spot and pre-empt violent right-wing extremists like the ex-soldier who shot up a Wisconsin Sikh temple face serious legal and political hurdles, including free speech guarantees and pushback from political lobbies.
Officials and private experts who track extremists groups say US laws, particularly the First Amendment to the US Constitution, prevent official investigators from bringing cases against Americans for having extreme beliefs.
And past attempts by the US government to highlight the threat of right-wing extremism have provoked a political backlash, further complicating attempts to deal with the issue.
After the leak of a 2009 Department of Homeland Security report that noted the potential radicalisation of US military veterans, conservative activists complained that it defamed the troops. DHS was forced to apologise for the document and disband the unit that produced it.
The Wisconsin shooter, Wade Page, was a military veteran, although he had been discharged years ago, in 1998. US officials confirmed government agencies over the past several years received reports linking Page to white supremacist groups.
Two private groups that monitor extremist movements, the Southern Poverty Law Center and the Anti-Defamation League of B'nai Brith, said they had also collected information about Wade's involvement with extremists, including pictures of tattoos linking him to a racist group called the Hammerskins.
But even in such cases, US laws can make it difficult, if not illegal, for government agencies even to open investigations into people who express such views.
"We can't launch investigations based on free speech," a federal law enforcement official said. If federal investigators did investigate an individual for merely expressing extremist views, the official said, "they could get into trouble."
In contrast, laws in some European nations proscribe and even criminalise various forms of "hate speech." German law bans "incitement of popular hatred."
In Britain, the former captain of England's national soccer team was recently put on trial for allegedly hurling a racist taunt at a rival player. He was subsequently acquitted.
In Page's case, "I don't think law enforcement could have done any more than they did do to stop this," said Mark Potok, a veteran investigator of Far Right groups with the Southern Poverty Law Center.
Racist Rock Band
While there was information out there that Page might have "said vile things ... the activities of this man were totally legal," Potok said. "There was no indication that this guy was going to carry out a mass murder."
Mark Pitcavage, an investigator for the Anti-Defamation League (ADL), said his organisation had been aware of "Definite Hate," a racist rock band in which Page played, for several years. But ADL did not focus on Page until about 2010.
Even when ADL started paying more attention to Page, Pitcavage said, there was little to indicate he was on the verge of committing violence, let alone mass murder.
"I can't fault federal or local law enforcement for not picking up that he was a loose cannon," Pitcavage said.
He said Page moved to Wisconsin only recently, and that "lone wolf" extremists who move around the country are "the hardest to track. They're not around long enough (in one place) to call attention to themselves."
The Federal Bureau of Investigation is the lead federal agency in investigating cases of "domestic terrorism" and collecting intelligence on home-grown militants.
FBI spokesman Paul Bresson said it would not be "fair to say we focus more or less attention on a particular group. We investigate threats of criminal activity wherever it takes us."
But Bresson said that in pursuing such cases, the Bureau was obliged to be mindful of issues like freedom of speech.
"No matter how offensive to some, we are keenly aware that expressing views by itself is not a crime and the protections afforded under the Constitution cannot be compromised," he said.
Some government officials who tried to call attention to what they perceived to be a growing threat from right-wing extremists felt badly burnt after the Department of Homeland Security publicly disavowed the 2009 study they had produced.
The paper, entitled "Rightwing Extremism: Current Economic and Political Climate Fueling Resurgence in Radicalisation and Recruitment," was produced by a group of analysts attached to the department's intelligence and analysis office.
In hindsight, the paper seems prophetic. It said that right-wing extremists had "capitalised on the election of the first African-American president, and are focusing their efforts to recruit new members, mobilise existing supporters, and broaden their scope and appeal through propaganda," though it noted "they have not yet turned to attack planning."
The paper also asserted that "the return of military veterans facing significant challenges reintegrating into their communities could lead to the potential emergence of terrorist groups or lone wolf extremists capable of carrying out violent attacks."
It devoted several paragraphs to "Disgruntled Military Veterans," whose skills and knowledge, it said, "have the potential to boost the capabilities of extremists - including lone wolves or small terrorist cells - to carry out violence."
After the paper was leaked, criticism from conservative commentators became so intense that Janet Napolitano, the Homeland Security Secretary, publicly apologised.
In the wake of the controversy, Homeland Security disbanded the small team of analysts assigned to study "domestic non-Islamic extremism," which had produced the report. Much larger teams of analysts at the department were assigned to sort through information about Islamic militants.
Daryl Johnson, the former official who ran the team, told Wired Magazine's Danger Room blog this week his team had been "dissolved," and that Homeland Security was "scoffing at the mission of doing domestic counter-terrorism, as is Congress."
One senior law enforcement official, speaking on condition of anonymity, insisted US agencies are still seriously engaged in assessing potential threats from both violent right-wing extremists and Islamic militants.
Even though Homeland Security's intelligence office underwent a "restructuring" after the 2009 report came out, the official said, it continues to study and produce papers on right-wing threats.
These include white supremacists and "sovereign citizens," a genre of extremists who refuse to recognise the US government, often use fraudulent identification and financial documents, and sometimes react violently when challenged.
Homeland Security also produced a detailed study of Anders Behring Breivik, the gunman who killed more than 70 people in Norway last year. The study aimed to examine whether, in hindsight, there were indicators in the behavior of a "lone wolf" like Breivik that could have enabled authorities to spot and prevent his descent into violence.
Because lone-wolf attackers like Page are the hardest to spot in advance, federal officials and private monitoring groups say they are expanding efforts to educate state and local law enforcement authorities on danger signs to look for.