If Cho Seung-Hui had been a warning light, he would have been blinking bright red.

Two female students complained to campus police that he was stalking them. His poetry was so twisted that his writing professor said she would quit if he weren't removed from her room. Some students found him so menacing that they refused to attend class with him.

Yet Virginia Tech, like other colleges trying to help emotionally troubled students, had little power to force Cho off campus and into treatment.

"We can't even pick up the phone and call their family. They're adults. You have to respect their privacy," said Brenda Ingram-Wallace, director of counseling and chair of the psychology department at Albright College in Reading.

In the aftermath of the deadliest shooting in U.S. history, counselors, police authorities, and mental-health professionals say privacy laws prevent colleges from taking strong action regarding students who might be dangerous.

Many at Tech saw Cho as a threat - and shared those fears with authorities. In 2005, after the second stalking complaint, the school obtained a temporary detention order that resulted in Cho undergoing a psychiatric evaluation. But the 23-year-old remained enrolled at the university until the moment he shot himself to death.

Federal laws such as the 1974 Family Educational Rights and Privacy Act (FERPA) and the 1996 Health Insurance Portability and Accountability Act (HIPAA) protect students' right to privacy by banning disclosure of any mental-health problems - even to family members - without a signed waiver.

Patient-therapist confidentiality is crucial, privacy advocates say. Students may shy from treatment for fear of exposure.

FERPA does allow colleges to release information without permission in cases of "health and safety emergencies." But the criteria are so vague, and the potential liability so severe, that administrators say they hesitate to act in any but the most dire circumstances.

"The law tends to be protective of individual autonomy rather than getting in there and forcing people to get treatment," said Anthony Rostain, associate professor of psychiatry at the University of Pennsylvania School of Medicine.

Lots of students write violent stories, he noted. How do you distinguish between a future Cho Seung-Hui and a future Quentin Tarantino?

"This kind of problem happens all the time across college campuses," Rostain said.

The law puts colleges in a tough position, said Dana Fleming, a lawyer with the college and university practice group at Nelson, Kinder, Mousseau & Saturley in Manchester, N.H. Schools may face legal trouble if they try to keep ill students out, if they try to send them home, or if they let them stay.

"No matter which decision they make," she said, "they can find liability on the other end."

Colleges can't screen students for mental illnesses during the admissions process because that violates the Americans With Disabilities Act. As a result, schools know which students will need tutoring or want to play soccer, but have no idea who is likely to need mental-health care, Fleming said.

Virginia Tech and most other universities cannot summarily suspend a student. Formal disciplinary charges must be filed and hearings held. Students who initiate a complaint often end up dropping the matter.

Nor can schools expect courts to hospitalize a student involuntarily without solid evidence that he poses a danger to himself or others.

That has left many colleges trying to find creative ways to identify and help troubled students.

At Albright College, administrators recently updated a program where anyone concerned about a student's behavior - a work supervisor, a professor or another student - can fill out a "student alert form."

Perhaps friends notice a student has become withdrawn or has stopped showing up for class. If multiple forms arrive concerning the same person, counseling director Ingram-Wallace said, the counseling center investigates by contacting housing officials or by reaching the student via phone or e-mail.

But the choice to speak with a psychological counselor stays with the student. The center can't send a therapist to knock on the student's door, she said.

"On the surface, it sounds like a caring thing to do," she said, but "if they haven't been dangerous to themselves or others, there's no reason to mandate them into any kind of services."

Among students who have been referred to the counseling center, "the responses are mixed," she said. "Some people felt imposed upon."

At St. Lawrence University in Canton, N.Y., every student who visits the health center - even for a head cold - is screened for depression and signs of other mental illness. The effort follows a national study that showed depression rising among college students.

If a screening shows someone needs help from the health center, "we literally walk them over there," said Patricia Ellis, director of counseling services.

More than a year before Monday's massacre of 32 students and staff members, Cho was twice accused of stalking female students and taken to a mental-health facility amid fears he was suicidal, police said yesterday.

After the first incident, in November 2005, police referred him to the university disciplinary system. Ed Spencer, Tech's assistant vice president of student affairs, said he could not comment on any proceedings against the gunman because federal law protects students' medical privacy even after death.

The university obtained the detention order after the second stalking complaint, in December 2005. "His insight and judgment are normal," an examiner at the psychiatric hospital concluded.

Yet poet Nikki Giovanni, one of his professors, told CNN that students were so unnerved by Cho's behavior, which included taking cell-phone photos of them in class, that most stopped attending the course. She insisted that he be removed.

Lucinda Roy, a codirector of the creative writing program, tutored Cho after that, and tried to get him into counseling. He always refused. Roy sent samples of Cho's writing, with its images of people attacking each other with chain saws, to the campus police, student-affairs office, and other agencies.

All were sympathetic, she said, but little could be done. The writings contained no direct threats.

Contact staff writer Jeff Gammage at 610-313-8110 or jgammage@phillynews.com.

Inquirer staff writer Paul Nussbaum contributed to this