Justice Hemant Kumar Srivastava rejected the bail plea saying he was not inclined to consider the application after going through the FIR and other documents in the murder case.
The judge, however, said he would consider the bail plea if the CBI court failed to complete the trial within six months.
The BJP MLA was stabbed to death at his ancestral residence in Purnia on January 4 allegedly by Pathak, who was arrested soon after the incident.
The state government had recommended a CBI probe into the murder following a hue and cry raised by the Opposition. Pathak is presently lodged in Beur jail.