When the second semester begins in April in the Catholic theology department of Tuebingen University, Swiss theologian Hans Kung will return to deliver his provocative lectures to an invariably crowded classroom.

"I have no intention of giving up my duties as priest and theologian or of leaving the church," the embattled critic of the Vatican declared. "I remain a member of the loyal opposition."

"I can fight them in the courts until I'm near retirement," the 51-year-old priestem in the courts until I'm near retirement," the 51-year-old priest-professor added. The education ministry of the state of Baden-Wuerttemberg is awaiting a legal opinion before acting on the Catholic Church's request to have Kung removed from the Catholic theology faculty, now that the Vatican has ruled he can no longer be considered a Catholic theologian.

To give up the fight to retain his place in the Catholic department of the state-run university would disillusion many of his supporters, said Kung, who has taught here for 20 years.

Some of Kung's support recently eroded when seven of 12 full professors in the Catholic religion faculty accused him of undermining the status of the department by staying on without the Vatican's blessing.

Professor Walter Kasper, one of the seven, said the statement was intended to encourage Kung to moderate his outspokenness and to seek reconciliation with the Vatican. "We want Kung, but with the mission [teaching authority]," he explained.

The seven were critical of Kung's "propaganda campaign," his criticism of the papacy and the church's investigation methods and of his vow to fight the ouster through the courts. "If this all continues any further," one of the professors warned, "only the broken pieces will be left over."

A month ago, the faculty had voted -- with only two dissents -- to urge university officials to use all legal means to keep the well-known theologian in the department.

Kung relies on considerable support from his students, from liberal clergy and from the laity, and is a popular man in this community, where thousands signed protest petitions on his behalf.

Through his prolific writings, lectures, and TV talk show appearances, Kung has become a symbol to liberal Catholics of intellectual resistance to the conservatism of Pope John Paul II.

His censure also reflects a conservative trend within the present West German Catholic leadership, which had buffered him from Vatican action for nearly a decade.

Kung claims the December decision of the Vatican's Sacred Congregation for the Doctrine of the Faith was motivated in part by a critical newspaper article he wrote last fall on Pope John Paul's first year.

The wary-haired theologian, who favors a coat and tie or turtleneck sweater instead of a cassock, maintains that the Vatican's investigation denied him a chance to present his case in person. He likened his case to Soviet dissidents banished by the Kremlin.

"A common criminal has more rights than a Catholic theologian," he said in the kind of hyperbole that has alienated some fence-sitters. Critics also accuse him of playing the role of media star, with an affinity for the spotlight.

While Kung recently told a student gathering that he was "just a simple theologian," he also has compared his latest book, "On Being a Christian," with the work of the classic Catholic scholar Thomas Aquinas.

When Kung told Cardinal Josef Hoeffner, head of the West German bishops' conference, that "I have truly performed a tremendous task -- I say that in all modesty -- to make Christianity more understandable to the people of today," that stirred concern among the conservative sector of West German Catholicism, both for its tone and implications.

Hoeffner charged that Kung had avoided a dialogue with West German and Swiss bishops, insisting on direct talks with the pope in an open hearing in Rome. The German bishops, after meeting with Pope John Paul following the decree, agreed that the ban should stand.

The German church has moved in recent years to purge liberals, leftists and mavericks from the teaching and administrative ranks (the most frequent target: lay employes living out of wedlock). At least four priests lost university theology positions when they married, and liberal theologians approved by the university for jobs have been blackballed by conservative prelates.

An onimous precedent for Kung occurred in 1975 when Professor Horst Herrmann lost his chair in the Catholic theology department at the university of Muenster for failing to abide by church dogma.

Like Herrmann, Kung could continue as a lecturer in the sociology department or in the Protestant faculty. Seminarians of both Christian faiths study at Tuebingen, an early Lutheran stronghold that has a long tradition of theological coexistence and cooperation. Kung also heads the university's Institute for Ecumenical Research.

But the feisty Swiss clergyman is prepared to argue his case through the courts, dragging out a list of Vatican irregularities that is certain to cause further controversy.

In a university lecture on why he remains a Catholic in spite of the teaching ban, Kung argued that he remains true to the historical tradition and worldwide scope of Catholicism.

But as an inquiring academic, he said that preaching complete acceptance of everything within the church and from Rome is a disservice to the faithful.

"Not everything that has been officially taught and practiced in the Catholic church is truly Catholic," Kung said.

After the Vatican decided to suspend his teaching credentials, Bishop George Moser of Rottenburg-Stuttgart, long a supporter of Kung, informed the Baden-Wuerttemberg state education department that the professor has no longer qualifed as a Roman Catholic instructor at the university.

But State Education Minister Helmut Engler is investigating the legal foundations before taking any action.

Engler and Moser have been trying to reach a compromise. "If Bishop Moser modifies the withdrawal of the church's teaching credentials for Hans Kung, it would produce a different legal opinion for us also," Engler pointed out.

Kung readily admits that the Vatican could strip him of the priesthood. deny him the right to preach, condemn his books and even excommunicate him. That might end the sticky legal question but would raise a further whirlwind of controversy.

Kung is insistent in his petition, however: "Rome can't go back and neither can I. I have my own stand and to move me will be difficult."