The American Civil Liberties Union and the state of New York yesterday filed a lawsuit seeking to overturn the Justice Department's decision to classify three Canadian films as "political propaganda."

The suit also seeks to strike down the film-labeling provisions of the Foreign Agents Registration Act. Under those provisions, films that are designated as political propaganda must carry a disclaimer stating that the U.S. government does not necessarily approve of their content, and film distributors must supply the names of theaters or groups that show the films.

Attorneys for the ACLU and the Environmental Defense Fund, which is a party to the suit, said Justice's decision to require such labels on two acid rain films and a nuclear war documentary produced by the National Film Board of Canada is a violation of free speech and "stigmatizes" the films.

The suit was filed jointly by the state of New York, which wants to use the acid rain films in its public education programs. Other plaintiffs are the U.S. distributor of the nuclear war film, the Biograph Theatre in Georgetown, which has shown the films, two environmental organizations and the New York Library Association.

In a letter to editors and reporters last week, Justice spokesman Thomas P. DeCair defended the decision, saying that the administration simply was enforcing the provisions of the 45-year-old foreign agents act.

"If anyone disagreees with the rquirements of the act, he should look to Congress, not to the Department of Justice," DeCair said.