Discrimination against Western newspapermen by radicals in nominal control of revolutionary Iran is now being used to deny visas, suggesting a renewed and disturbing trend by anti-American regimes toward controlling the flow of news.

Iran was to be a principal goal in the itinerary of our latest trip to the Persian Gulf area -- but we will not be going there because the revolutionary high command has refused us a visa.

No coherent explanation was officially supplied, anymore than was supplied by Uganda (under Idi Amin) and Mozambique in 1977 or communist Vietnam in 1978 when those countries denied us visas. The only difference with Iran is that we learned (through an intermediary) the real reason: what we have written in the past has displeased the Revolutionary Council.

That destroys the old rule of thumb that a reporter rates entry to a foreign country if he meets three tests: represents a bona fide publication, adheres to the laws of the land and agrees to pay his bills. The new test goes to the question: what does he think? Or, at least, what does he reveal publicly about what he thinks?

The problem is profound. If a reporter is barred from Iran because of what he has written, that implies a test on what is written by reporters who are admitted.

A year ago when demonstrators roamed the streets of Tehran demanding the shah's head,American journalists were prized as an essential conduit for their views. We obtained an Iranian visa last April.

But affection for the U.S. media cooled after Ayatollah Ruhollah Khomeini took power and reporters wrote of political repression. (We reported from Tehran that grave economic and political disintegration had set in and would worsen.) In September, the Associated Press bureau was shuttered and those AP reporters expelled. Seven other Western newsmen were kicked out. An interview at the embassy in Washington became a prerequisite for a journalist's visa.

After terrorists seized the U.S. Embassy, Khomeini's regime again welcomed American newsmen to tell its story -- up to a point. We discovered that point when, after applying for a visa, we were interviewed by Iranian press attache Hussein Ava. Ava cared deeply about what we thought.

"Is not the United States government responsible for the shah's mass murder and torture of the Iranian people?" he asked. We replied that the United States a generation ago had put the young shah in power but that we had heard only allegations about "mass murder" or "torture."

"You have been all these years a newspaperman and do not know facts that all the world knows?" Ava asked. Were we censored by the Carter administration or our bosses? No, we replied. "Well," Ava said, "other journalists who have been in here tell me that they have." He lectured at length on alleged distortions of news from Iran by the U.S. media.

Three days later, the Iranian Embassy told us the visa application had been denied. Ava's explanation: too many Western newsmen in Tehran.

The real story emerged when James Abourezk, a former senator from South Dakota and now a Washington lawyer representing Iran's government, returned from Tehran. At our request, Abourezk graciously asked what had happened to our visa application. "They told me," he soon reported back, "that you had written the worst stuff about Iran of anybody and you weren't getting any visa." His suggestion that we be given an opportunity to see the situation firsthand got nowhere.

This is a familar problem for American foreign correspondents, such as William Shirer, who sent courageous radio reports for CBS out of Berlin in Nazi Germany. Many U.S. newsmen have been kicked out of the Soviet Union for reporting the truth. The threat is implicit in Tehran today.

That may explain why correspondents in Tehran have persisted in referring to trained terrorists as "students." The new acting foreign minister, Sadegh Ghotbzadeh, who is notoriously anti-American, was described in these terms by one network correspondent: "In the opinion of those who know him personally, Ghotbzadeh is a moderate who will nevertheless faithfully execute the decisions of Ayatollah Khomeini." The regime in Tehran is clearly in a discriminating mood about who shall be permitted to make such assessments.