A US federal judge has ordered the release on compassionate grounds of three men convicted in a case that became known as the "Newburgh Four", in a severe rebuke of the FBI's use of an informant in an "unscrupulous" operation to persuade the men into committing a violent plot to blow up synagogues and shoot down National Guard planes.

In a scathing rebuke against the FBI, US District Judge Colleen McMahon said that the men - Laguerre Payen, Onta Williams, and David Williams - were "in reality, hapless, easily manipulated and penurious petty criminals".

The fourth individual, James Cromitie, did not seek compassionate release and is expected to serve until 2030. However, his lawyer told the Associated Press she plans to speak with him about pursuing similar action on his behalf.

McMahon's 28-page ruling, released on Thursday, went on to say that all four men were caught up in a 2009 plot that was driven by Shahed Hussain, a confidential informant described by the judge as "unsavory", and overzealous FBI agents.