City Sessions Court Chief Judge Kundan Kumar Kumai discharged Gurung from the case rejecting the CBI's contention that the Gorkha Janmukti Morcha (GJM) chief was involved in the conspiracy to murder the All India Gorkha League leader, one of his political opponents in the Darjeeling hills.
The court, however, directed that charges be framed against all other 47 accused, including Gurung's wife Asha and several other top leaders of GJM.
It fixed August 28 for framing of charges against the accused persons.
The counsel for Gurung had claimed that he was in Kalimpong on the day of the death and that the CBI could not provide any proof that he was involved in the conspiracy to kill Tamang.
The CBI had filed cases against all the accused persons for murder and criminal conspiracy. It had claimed that it was a premeditated murder to prevent any other political party from holding meetings or rallies in Darjeeling hills, where the GJM held sway through "coercive" measures.
Tamang was attacked with sharp weapons when he was overseeing preparations for a public meeting at Clubside in the heart of Darjeeling town on May 21, 2010, and was declared brought dead at the sadar hospital there.
All the accused had filed discharge petitions before the court, which passed the order after hearing their advocates and that of CBI for several days.
The CBI opposed the discharge petitions and prayed for framing of charges against the accused.
The Supreme Court had on October 8, 2013, directed transfer of hearing in the case from Darjeeling sadar court to the city sessions court here on a petition by Tamang's widow Bharati.
She had claimed that witnesses could be impacted if the trial was held in Darjeeling.