PITTSBURGH — A central Pennsylvania man has sued police who charged him with flag desecration for painting the letters “AIM” on an American flag that he flew upside down on his house as part of a Native American protest.

Joshuaa Brubaker, 39, is part Native American and says “AIM” stands for the American Indian Movement. Brubaker flew the flag on his porch in Allegheny Township in May 2014, about 90 miles east of Pittsburgh. He was protesting plans to route the proposed Keystone Pipeline through Wounded Knee, S.D.

Wounded Knee is the site of a U.S. Calvary massacre of some 200 Lakota Indians in 1890 and, in 1973, the Indian reservation town of the same name was seized by AIM and other activists in a 71-day standoff with the federal law enforcement.

“The Supreme Court has said that individuals have the right to use the American flag to protest, even if some people might think it’s being used in a disrespectful manner,” said Sara Rose, one of the American Civil Liberties Union attorneys who filed the federal lawsuit on Wednesday. “Here, clearly our client was using it for political expression.”

Brubaker contends the township, and its police chief, Leo Berg III, were wrong to seize the flag and charge him. A Blair County judge dismissed the criminal charges last year, saying Brubaker’s protest was constitutionally protected speech — which Brubaker’s lawsuit echoes.

Brubaker told The Associated Press that he hoped the flag would call attention to issues AIM champions, and draw attention to his Facebook page, on which he posts about issues of interest to the group.

“I figured with this generation, if someone drove by this house and saw AIM” that they’d Google it and learn more about the group and its causes, Brubaker said. Flying a flag upside down is also a distress signal, and Brubaker believes the country is in distress over such issues and others.