By Jonathan Stempel

Dec 6 (Reuters) - A federal appeals court on Thursday upheld the conviction of a California man for sparking a nationwide anthrax hoax in 2008, saying his mailings of sugar packets labeled as anthrax did not qualify as free speech. It also ordered that he be resentenced.

The 9th U.S. Circuit Court of Appeals in San Francisco said a federal jury properly convicted Marc McMain Keyser in September 2009 over mailings received by a Starbucks store and McDonald's restaurant in his hometown of Sacramento, California, and by an office of George Radanovich, then a congressman from California.

According to court papers, Keyser sent roughly 120 packages to politicians, media and businesses containing a CD with excerpts from his book "Anthrax: Shock and Awe Terror" and a white sugar packet labeled "Anthrax" and "Sample," with an orange biohazard symbol.

In his appeal, Keyser, 70, said that in showing the vulnerability of the United States to an anthrax attack, his mailings qualified as political speech under the First Amendment to the U.S. Constitution and were not "true threats."

The 9th Circuit disagreed. "A reasonable sender would foresee that recipients would understand the mailings to be threats to injure them," Circuit Judge Richard Clifton wrote for a unanimous three-judge panel.

The court nonetheless said that in sentencing Keyser to 4-1/4 years in prison, the trial court improperly considered the government's costs to respond to other mailings for which Keyser was not convicted. It ordered the trial court to resentence him.

"We're really disappointed with the decision" and will review what action to take next, Keyser's lawyer John Balazs said in an email. Keyser is housed in a low-security prison in Lompoc, California, federal prison records show.

The case is U.S. v. Keyser, 9th U.S. Circuit Court of Appeals, No. 10-10224.

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