* 9th Circuit votes 7-4 to overturn prison sentence
* Ressam was convicted in Los Angeles airport plot
By Dan Levine
SAN FRANCISCO, March 12 (Reuters) - A U.S. appeals court on Monday overturned the 22-year prison term of the "Millennium Bomber," saying it was too lenient, and sent the case back to a lower court for re-sentencing.
Ahmed Ressam was arrested in connection with a plot to detonate explosives at Los Angeles International Airport in 1999 and sentenced to a 22-year prison term plus five years of supervised release. But prosecutors appealed the sentence, imposed by a Seattle-based federal judge, as too lenient.
A split 11-judge panel of the 9th U.S. Circuit Court of Appeals vacated the sentence on Monday, the latest turn in a case that has been litigated for years. The appeals court voted 7-4 that Ressam's prison term was much shorter than that called for by U.S. sentencing guidelines.
The ruling largely upholds an earlier opinion by a three-judge 9th Circuit panel in 2010.
Ressam's attorney, Thomas Hillier, said the latest ruling is a slight improvement compared to the one from 2010, which had removed the original sentencing judge, who has now been returned to the case.
The judge, U.S. District Judge John C. Coughenour, had written newspaper opinion pieces to argue that the federal courts were the appropriate place to try accused terrorists, as opposed to military tribunals.
Ressam has been incarcerated since his arrest in 1999, Hillier said.
"The majority believes the sentence was too low and the majority rules," Hillier said.
Ressam, trained in terrorist camps in Afghanistan, had planned an attack for Dec. 31, 1999, according to the opinion. But he was apprehended shortly beforehand while crossing the border from Canada into the United States, and a jury convicted him in 2001.
He later reached a deal with U.S. federal prosecutors to give information about other terrorism suspects in return for a shorter sentence. But Ressam angered prosecutors by refusing to cooperate further after early 2003.
Emily Langlie, a spokeswoman for the U.S. Attorney's office in Seattle, said prosecutors "will seek to hold Mr. Ressam fully accountable for his attempt to murder scores of innocent people by bombing the Los Angeles airport."
The explosives found in Ressam's possession were capable of producing a blast 40 times greater than that of a devastating car bomb, 9th Circuit Judge Richard Clifton wrote in the opinion.
"The crimes that Ressam sought to commit were horrific," Clifton wrote. "The most important reason for our conclusion that the sentence imposed by the district court was substantively unreasonable is that the sentence did not properly account for those crimes."
In dissent, Judge Mary Schroeder wrote that it was reasonable for the district court to credit Ressam's cooperation.
"Although the end of Ressam's cooperation burdened the government's ability to pursue several criminal prosecutions," Schroeder wrote, "he provided a wealth of information otherwise not susceptible to later recantation or retraction."
Ressam is currently serving his sentence at the "Supermax" federal prison in Florence, Colorado, according to the Federal Bureau of Prisons.
The case in the 9th Circuit is United States of America v. Ahmed Ressam, 09-30000.