Sgt. Gary Stein will get an other-than-honorable discharge and lose most of his benefits for violating the policies, the Corps said.
Stein started a page called Armed Forces Tea Party on Facebook that encouraged service members to exercise their free speech rights. The Marine Corps decided to take action after a post in which Stein said he would not follow what he called unlawful orders from the president.
Stein, who has served nearly 10 years in the Corps, said he was disappointed by the decision. He has argued that he was exercising his free-speech rights.
The military has had a policy since the Civil War limiting the free speech of service members, including criticism of the commander in chief. The policy states military personnel in uniform cannot sponsor a political club; participate in any TV or radio program or group discussion that advocates for or against a political party, candidate or cause; or speak at any event promoting a political movement.
Marine Corps Capt. John Torresala told a military panel that Stein acted irresponsibly and disregarded repeated warnings that his anti-administration postings violated Pentagon policy. Prosecutors say Stein sold "Nobama" stickers online and even shared images with Mr. Obama's face on a poster for the movie "Jackass."
Stein's attorney, Gary Kreep, said he would pursue administrative appeals within the Marine Corps but anticipates the effort will be denied. He said he planned to file an amended complaint in federal court.
The Associated Press contributed to this report.