LEADERS of the sanctuary movement are embarked on a heavily political mission. They seek to do more than shelter and feed Salvadoran refugees, which would not violate any American law. Instead, by organizing thousand-mile car caravans and calling press conferences, they publicize the fact that they are transporting undocumented aliens in furtherance of their evasion of the immigration laws, and that is a violation. The movement wants to accomplish two objectives: a change in the immigration laws that will allow undocumented Central Americans to remain here indefinitely and an end to U.S. intervention in Central America.

For two years the movement was all but ignored by the Immigration and Naturalization Service. There are millions of illegal aliens here, and immigration officials in the Southwest estimate that 3 or 4 million more avoid apprehension at the border each year. About half a million of these aliens are Salvadorans, but the sanctuary movement has aided only a few hundred. Recently, though, there have been some arrests. One movement worker was convicted of transporting an illegal alien and sentenced to two years' probation; another was acquitted of similar charges recently; 16 more, including three Roman Catholic nuns, two priests and a Presbyterian minister, have been indicted.

At his trial in Corpus Christi, Tex., recently, Jack Elder, a sanctuary worker, claimed that the First Amendment barred his prosecution, since his actions had been based on his religious beliefs. This argument -- which might also be made by abortion clinic bombers or polygamists, for example -- is a bad one, and it was rejected by the court. Nevertheless, Mr. Elder was acquitted by a jury -- though a co-worker was convicted some months ago -- which may demonstrate a growing sympathy for the objectives of the movement.

In the months ahead, in public forums and at the trials to come, public debate on this issue will increase and important questions will be considered. Are we treating all potential refugees equally, or do we give preference to those -- from Poland and Afganistan, for instance -- fleeing from regimes we dislike? How many of the millions of Central Americans who want to come here can we take in? Are they, in fact, political refugees? Or have they chosen to come for economic reasons, in which case they must wait their turn and come as ordinary immigrants? The sanctuary movement is forcing us to confront again these difficult political questions.