When Wendy Gonaver was offered a job teaching American studies at California State University, Fullerton, this academic year, she was pleased to be headed back to the classroom to talk about one of her favorite themes: protecting constitutional freedoms.

But the day before class was scheduled to begin, her appointment as a lecturer abruptly ended over just the kind of issue that might have figured in her course. She lost the job because she did not sign a loyalty oath swearing to “defend” the American and California constitutions “against all enemies, foreign and domestic.”

As a Quaker from Pennsylvania and a lifelong pacifist, Ms. Gonaver objected to the California oath as an infringement of her rights of free speech and religious freedom. She offered to sign the pledge if she could attach a statement expressing her views, a practice allowed by other state institutions. But Cal State Fullerton rejected her and insisted she sign the oath if she wanted the job.

“I wanted it on record that I am a pacifist,” Ms. Gonaver, 38, said. “I didn’t expect to be fired …”

University officials say they were simply following the law and did not discriminate against Ms. Gonaver because all employees are required to sign the oath. A California State University spokeswoman, Clara Potes-Fellow, said the university does not permit employees to submit personal statements with the oath.

“The position of the university is that her entire added material was against the law,” she said.

The loyalty oath was added to the state Constitution by voters in 1952 to root out communists in public jobs. Now, 16 years after the collapse of the Soviet Union, its main effect is to weed out religious believers, particularly Quakers and Jehovah’s Witnesses.

In February, another California State University system instructor, Marianne Kearney-Brown, a Quaker math teacher, was fired because she inserted the word “nonviolently” when she signed the oath. She was quickly rehired after her case attracted the attention of the press.

Public agencies do not appear to keep a record of people denied employment over the oath. Union grievances and lawsuits are rare.

Some agencies take the oath more seriously than others. Certain school districts and community colleges have been known to let employees change the wording of the oath when they sign or to ignore the requirement altogether. Others advise employees on how they can register their objections yet still sign the pledge. The California State University system takes a firmer approach.

All state, city, county, public school, community college, and public university employees — about 2.3 million people — are covered by the law, although noncitizens are not required to sign.

The University of California, Berkeley, was the first to impose a tough anti-communist loyalty oath in 1949 and fired 31 professors who refused to sign.

After a version of the oath was added to the state Constitution, courts eventually struck down its harshest elements but let stand the requirement of defending the constitutions. In one court test, personal statements accompanying the oath were deemed constitutional as long as they did not nullify the meaning of the oath.

Ms. Kearney-Brown said she believed she was defending the Constitution by objecting to the oath.

“The way it’s laid out, a noncitizen member of Al Qaeda could work for the university, but not a citizen Quaker,” she said.

For Ms. Gonaver, the oath came up unexpectedly.

She was offered the job at Fullerton to teach two classes last fall. She received two appointment letters and signed a contract. When she attended an orientation session for new faculty, she heard of the oath for the first time.

After researching the issue and learning that the University of California system allowed its employees to provide personal statements, she submitted her own six-sentence declaration to Fullerton.

In her statement, she wrote that the oath violates the First Amendment and discriminates against religious pacifists. She called the pledge an “instrument of intimidation.” And she wrote that employees who sign the oath “while harboring legitimate religious and political objections” could be exposed to a charge of perjury.

The Fullerton school’s associate vice president for academic affairs, Margaret Atwell, replied in an e-mail that Ms. Gonaver was not allowed to submit any statement, no matter what the practice in the University of California system. Ms. Gonaver would have to sign the oath or lose the job.

Ms. Gonaver refused.

“It makes no sense … ,” she said. “It’s people who take it seriously who don’t get hired.”