The Vatican's decision to force an American nun to leave her order after she refused to publicly denounce Medicaid abortions has provoked extraordinarily strong protests from the leadership of American religious communities and their members. If the Vatican hoped that the matter of Sister Agnes Mary Mansour would quietly go away, it badly miscalculated the assertiveness of the modern American nun.

Mansour left the Sisters of Mercy last week after the Vatican informed her she would be ousted from the order unless she resigned from her job as Michigan's director of social services.

The Leadership Conference of Women Religious, which includes about 90 percent of the superiors of American orders, announced that it was "grieved and shocked at the way the Mansour case has been concluded. That a woman who has devoted thirty years of service to the church . . . should find herself acting under duress to request dispensation from her vows is incomprehensible to us."

The National Assembly of Religious Women and the National Coalition of American Nuns, groups that represent about 3,800 nuns committed to social justice, expressed their "deep concern and sadness at the unjust treatment of a sister," who was forced out without "option or dialogue." The groups called upon women "to gather in silent prayer" this Sunday "as a visible witness to the arrogant use of power in a male-dominated church." Protests are scheduled in a number of major cities, including Washington.

The board of NETWORK, a social justice lobby founded by nuns, said it "deeply regrets the authoritarian exercise of administrative power on the part of Vatican officials."

The Vatican's treatment of Mansour and her order raises important questions about the rights of American nuns in their dealings with Rome. At stake is their ability to appeal Vatican decisions, the way women are treated by the church, and the issue of freedom of conscience in sensitive moral issues. It is also raising grave questions among progressive nuns about the limits they face when they decide to accept public policy jobs rather than limit themselves to service work.

There are about 120,000 nuns the United States, a figure that has steadily declined since the 1960s. The Sisters of Mercy, with about 9,000 members in its various communities, is among the largest of the orders.

"We are in perilous times when the church responds dictatorially, without regard for person, (or her vows,) or the ministry the sisters of Mercy have made for themselves, which includes political ministries and service to the poor," said Sister Donna Quinn of Chicago, president of the National Conference of Catholic Nuns. "Are we being asked to obey as people in a totalitarian state? Are we being asked to obey blindly, without dialogue, without due process, without the proper representation to officials of the Vatican? It tramples on who we are as women religious in the United States." She pointed to three recent cases involving priests who have questioned the church doctrine of infallability and who nevertheless remain in the priesthood.

"We see this as a real misuse of authority within the church of both personal rights and corporate rights" of the orders, said Sister Nancy Sylvester, national coordinator of NETWORK. "People are looking at this very seriously . . . as a watershed issue."

American priests and nuns have in recent years become more and more involved in such national issues as disarmament, human rights, and domestic priorities. The Catholic Church, however, is moving to restrict their opportunities to influence policy through the holding of legislative, judicial or administrative posts.

The church is on a collision course with Americans religious who are rejecting the idea of blind obedience to the Vatican and who want to participate in the affairs of humankind. It is clear from the sharp tone of the protests over the Vatican's treatment of the Mercy sisters that the American religious congregations are willing to go to considerable lengths to assert their worth, their rights, and their thoughts about how nuns should work and be treated in America. They are out of the convents just as other American women are out of the kitchens. The Mansour debacle illustrates the folly of trying to stifle their growth.

By attempting to diminish an American nun, the Vatican has suceeded only in diminishing itself.