Dr. Oxtoby said that when he heard the results, he “knew immediately this would be an explosive issue.”

“This is a very sensitive issue especially in Southern California, and many of our students and faculty are immigrants themselves or are descendants of immigrants,” he said. Still, he said, he had no doubt that the workers would need to leave the college. “The law is very unforgiving, and unfortunately we have to obey the law even though it really hurt the community.”

The idea that the college had mounted the effort to stop the union drive was the opposite of the truth, he said. “We’ve been trying to improve the relationship with workers for some time, and this has been a big setback,” Dr. Oxtoby said. “Rationally, it would have not made strategic sense.”

Dr. Oxtoby and the college’s trustees repeatedly said there was no choice but to fire the workers. In a letter from the law firm, lawyers for the college said the college would have left itself open to investigation and punishment from federal immigration authorities had it not fully examined the employment files.

Pomona is part of a consortium of seven colleges whose campuses intertwine here. In December, a day before the Pomona workers were fired, a human resources officer at Scripps College, another member of the consortium, called seven employees there asking them to complete a new work authorization form.

The next day, the Scripps president, Lori Bettison-Varga, sent an e-mail to students and the staff saying that “as soon as the calls came to the attention of the President’s Office, they were halted.” Further, she said that employment forms were stored off campus, and added, “There is no reason for any further questions or actions to be pursued.” A spokeswoman for the college said that the human resources official was not acting on any complaint.

That e-mail only prompted more anger and suspicion among those involved at Pomona, who argued that Scripps showed that the college could have taken less aggressive measures.