SAN DIEGO (AP) — The Marine Corps on Wednesday notified a sergeant who has been openly critical of President Barack Obama that he is violating Pentagon policy barring troops from political activities and that he faces dismissal.

Camp Pendleton Marine Sgt. Gary Stein started a Facebook page called Armed Forces Tea Party to encourage fellow service members to exercise their free speech rights. He declared a few weeks ago that he would not follow the unlawful orders of the commander in chief. Stein also criticized Defense Secretary Leon Panetta for his comments on Syria.

Stein, a nine-year member of the Corps, said he did nothing wrong and planned to fight the charges. He had applied to extend his service, which was set to expire in a few months.

"I'm completely shocked that this is happening," he said. "I've done nothing wrong. I've only stated what our oath states that I will defend the constitution and that I will not follow unlawful orders. If that's a crime, what is America coming to?"

The Marine Corps said in a statement Wednesday that Stein's commanding officer ordered a preliminary inquiry on March 8 after receiving allegations that Stein posted political statements about Obama on Facebook in violation of the Pentagon's directives.

"After reviewing the findings of the preliminary inquiry, the commander decided to address the allegations through administrative action," the Corps said.

Stein said in addition to being discharged, he would have his rank reduced to lance corporal if he is proven to be in violation of the rules. He said he was removed from his job at the Marine Corps Recruiting Depot in San Diego on Wednesday and given a desk job with no access to computers.

According to Pentagon directives, 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. Commissioned officers also may not use contemptuous words against senior officials, including the defense secretary or the president.

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In January, an Army reservist wearing camouflaged fatigues got into trouble for taking the stage during a rally in Iowa with Republican presidential candidate and Texas congressman Ron Paul.

Stein was first cautioned by his superiors at Camp Pendleton, north of San Diego, in 2010, after he launched his Facebook page and criticized Obama's health care overhaul. Stein volunteered to take down the page while he reviewed the rules at the request of his superiors.

He said he determined he was not in violation and relaunched the page. Last week, he said his superiors told him he could not use social media sites on government computers after he posted the message stating he would not follow unlawful orders of the president.

Stein said his statement was part of an online debate about NATO allowing U.S. troops to be tried for the Quran burnings in Afghanistan.

In that context, he said, he was stating that he would not follow orders from the president if those orders included detaining U.S. citizens, disarming them or doing anything else that he believes would violate their constitutional rights.

Another Marine alerted his command about the statement, Stein said.

Stein said he respects the office of the president, but he does not agree with Obama's policies. He said he is within his rights to speak up.

The Marine Corps said Stein is allowed to express his personal opinions as long as they do not give the impression he is speaking in his official capacity as a Marine.

Spokesman Maj. Michael Armistead said earlier this month that the Corps was taking a closer look to determine whether Stein had crossed that line.