Former Navy seaman Kristian Saucier, who was sentenced to one year in federal prison for taking pictures aboard a nuclear submarine in 2009, is suing former President Barack Obama and former FBI Director James Comey for unequal protection under the law.

Saucier alleges he was unfairly punished while former Secretary of State Hillary Clinton was left to walk for her unauthorized use of a private email server, the Washington Times reports.

President Donald Trump pardoned Saucier in March this year. Saucier's attorney says the lawsuit now plans to highlight the political nature of his client's prosecution compared to Clinton's.

In 2016, when Saucier's case was being litigated, prosecutors rejected any comparison to the Clinton case.

"The defendant is grasping at highly imaginative and speculative straws in trying to…draw a comparison to the matter of Sec. Hilary Clinton based upon virtually no understanding and knowledge of the facts involved, the information at issue, not to mention any issues if[sic] intent and knowledge," prosecutors wrote.

Furthermore, prosecutors said, "Saucier methodically documented the entire propulsion system of the nuclear submarine, including the design of its nuclear compartment and its nuclear reactor."

However, critics argue the most sensitive photos Saucier took contained Confidential information, which is the lowest tier of classified information.

Hillary Clinton's private email server, by contrast, contained at least eight email chains containing Top Secret information – the highest level of classification – and 36 containing Secret information – the middle level.

Clinton claims she did not knowingly send or receive classified information, while Saucier admitted knowing his conduct was illegal.

His lawyer wrote, "Mr. Saucier admitted that he knew when he took the pictures in 2009 that they were classified and that he did so out of the misguided desire to keep these pictures in order to one day show his family and his future children what he did while he was in the Navy."