When free speech falls on the cutting-room floor

The recent decision by the United States Justice Department to label three Canadian films as ''political propaganda'' is a disturbing development that inevitably will damage the free marketplace of ideas that has made America's democratic system healthy.

Groups that may want to screen these films may now hesitate to schedule them, because they will realize that their names and addresses will have to be supplied by the Canadians to the US government.

This can work against US films which are exported to Canada or other countries, often through the United States Information Agency. How will groups in other countries feel if they know that every American-made film they may look at will mean getting singled out by the justice departments of their own governments?

If this kind of action is permitted, where will it stop? Are the films I have produced - on precisely the same subjects as those three Canadian films - going to be next?

I recently completed ''Gods of Metal,'' which is about people in the US who are so concerned about their fear of the nuclear arms race leading to war that they are taking a variety of actions to express their concerns. ''Gods of Metal'' has been nominated for an Academy Award as best documentary short, as has ''If You Love This Planet,'' one of the Canadian productions rated ''political propaganda.''

''If You Love This Planet'' features Dr. Helen Caldicott, founder of the Physicians for Social Responsibility. She appears prominently in another film I am currently coproducing. Am I going to have to think twice about including her in the final production?

Two of the Canadian films are about acid rain. It happens that I produced ''What Price Clean Air?'' which PBS telecast nationally last summer. It focuses on acid rain as a scientific as well as political issue. Included in my documentary was Canada's environment minister, John Roberts, who states his government's views about acid rain which may originate from our Midwestern power-generating plants. I am now, because of the Justice Department's decision, wondering if the inclusion of Mr. Roberts in my film will jeopardize its exhibition in the future.

Additionally, I have seen one of the Canadian films on acid rain (''Requiem or Recovery''). It presents a scientific analysis of the issue, and is benign compared to some of the views expressed by people in my film. Perhaps I should start to tell those I interview in future productions to temper their views because the government of this great democracy is now having second thoughts about how much free expression we really are entitled to have.

There are hundreds of films that are shown in the US every year that originate in other countries. Many of them are undoubtedly advocating a point of view that is not necessarily endorsed by the Reagan administration's Justice Department. They are valuable for Americans to see for all kinds of reasons, not the least of which is to be exposed to diverse visions and viewpoints that will broaden the audience's perceptions of what the rest of the world is all about.