LAST NOVEMBER, in a most unreassuring, if vague provision, UNESCO's declaration on the mass media pledged to "protect" journalists. Who needed UNESCO's "protection"?-the question all but asked itself. And might this "protection" not turn out to be something self-respecting journalists would need to be protected from? Only four months later the gloomy answers are plain. The distinguished but muddled Sean MacBride, head of a UNESCO press commission, proposes to use the protection mandate to raise higher precisely the edifice of controls that Western-led protests tried to head off last fall.

Exactly who gets to be called a journalist? And who gets to do the calling? What are a journalist's rights? What are his duties? Mr. MacBride would have UNESCO, with its built-in Third World majority, address those questions and he would sanctify the answers in an annual press "round table." His proposal is a disaster.

The continuing effort by Third World ideologues and their trendy Western colleagues in UNESCO to grab hold of the world media is only half the story.Within the United Nations itself, a campaign is on to politicize the department of public information. A sprawling multi-media realm with a budget of $19 million and a staff of 600, this department constitutes a great global resource. It has served well in the past to publicize legitimate issues-food and population-and its professionalism is such that the film on the Palestinians it was instructed to produce two years ago was suppressed: It was too objective. All that may now change. The General Assembly has set up a review committee with 32 members from the Third World, 3 from the Soviet bloc and 6 from the West. Though the resolution establising the department enjoined it from conduting "propaganda," that is the direction the assembly apparently wishes the department to go.

Assaults on freedom of information have become a fixture of international life, a kind of cottage industry for disaffected Third World intellectuals and assorted political hangers-on. To work on improving the quality and usefulness of the media of other countries and on the free-press values implanted in the United Nations and its special agencies when they were founded. What might be called the anti-press states of the communist world egg the Third World on in this misshapen enterprise. It should be opposed by people everywhere who want information and debate from the press, not propaganda and mush.