'Determining responsibility for the steps taken on Nov 3, 2007 is necessary,' Chaudhry observed before issuing summons.

Chaudhry, who was one of the 80-odd Supreme Court and high court judges judges sacked, had been reinstated in March after a bruising lawyers' agitation.

Musharraf had sacked the higher judiciary after it refused to take fresh oath under the Provisional Constitutional Order (PCO) he promulgated along with the emergency Nov 3, 2007.

The emergency had been declared just as the Supreme Court was to deliver its verdict on the constitutionality of Musharraf's re-election in October 2007.

It had been contended that the same parliament and provincial assemblies that had elected Musharraf in 2002 had re-elected him in 2007 and this was unconstitutional.