A division bench of Justices A M Shaffique and Ashok Menon allowed the appeal by the five convicts, challenging the November 2015 verdict of the NIA court, sentencing them to varying terms of imprisonment.
Those acquitted are P A Shaduly, Abdul Rasik, Ansar Nadvi, Nizamudeen and Shammi.
The trial court had sentenced two of the accused to 14 years rigorous imprisonment (RI) and three others to 12 years RI, holding them guilty under various provisions of IPC and the Unlawful Activities (Prevention) Act.
The court had acquitted 11 others in the case.
The NIA court had also imposed a fine of Rs 60,000 each on two accused, while a penalty of Rs 55,000 was slapped on three others.
Books and pamphlets which were pro-Pakistan and anti-government, seditious and provocative in content with a view to create religious animosity were seized from their possession, it was stated.
The accused hailing from Idukki, Kottayam, Thrissur and Palakkad districts assembled at Pannyikulam for the 'secret' meeting, prosecution said.
The case was first probed by state police and later handed over to the National Investigation Agency (NIA), which filed a charge sheet in December 2011.
The charges were framed by the court in June 2014 and the trial commenced in July 2014.
The prosecution completed arguments in March 2015.
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