A University of Massachusetts decision this month to stop admitting Iranian nationals to certain engineering and science programs at its Amherst campus has stirred charges of discrimination and a backlash among students who say it was unfairly imposed and could hurt the school's reputation.

The dispute stems from the United States' efforts to prevent the Iranian government from developing a nuclear weapon, which prompted a 2012 law that excludes Iranian nationals from studying in America if they planned to work in nuclear or energy fields.

Enforcement of that law has generally rested with the State Department, which issues visas, and the Department of Homeland Security, which investigates threats. Generally, universities have depended on those agencies to weed out potential students seen as risks.

"We always felt like an integral part of the university community. Now we're just kind of confused"

But last week, the University of Massachusetts said that compliance with the government sanctions was getting increasingly difficult, and that it would simply bar all Iranian nationals from enrolling in certain graduate programs in its College of Engineering and College of Natural Sciences.

The university listed several examples, including physics, chemistry, microbiology, polymer science, chemical engineering, electrical and computer engineering, and mechanical and industrial engineering.

That appears to be a much broader ban than covered in the 2012 law.

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A State Department official told NBC News on Tuesday that "U.S. law does not prohibit qualified Iranian nationals coming to the United States for education in science and engineering. Each application is reviewed on a case-by-case basis. We will reach out to UMass Amherst to discuss this specific decision."

The new UMass policy, outlined in a document posted to the school's website Feb. 6, took students by surprise. In the days since, outrage spread among the school's small number of Iranian graduate students — who would not be affected by the ban, but would have to "certify their compliance" with the government restrictions — then to faculty and the outside world.

"We always felt like an integral part of the university community. Now we're just kind of confused," said Shirin Hakim, an Iranian-American who graduated last year and spoke on behalf of Iranian students still on campus. "We want an explanation for all this, and we don't think it should be tolerated, because it's clearly discriminatory against Iranian nationals."

Jamal Abdi, policy director of the National Iranian American Council, said his organization was working on a national petition to press the university to rescind the policy. He said he knew of only one other school, Virginia Commonwealth University, with a somewhat similar policy, albeit much less restrictive.

"The State Department and Department of Homeland Security really does cause headaches for these universities, but instead of allowing them to interview students and figure out which ones don't get a visa, the university is taking a short cut and policing it on their own," Abdi said. "That's discriminatory."

Emery Berger, a computer science professor, said his department wouldn't directly be affected by the ban, but he worried it would dissuade talented Iranians from seeking out the university as a place to conduct research.

"I think there is a reasonable risk that these students will look at this unfortunate set of affairs and conclude that UMass Amherst is not a welcoming place for Iranian nationals to go," Berger said. "Which is definitely not the case, except there is now this ridiculous policy."

The university has released a statement saying the ban was prompted by an inquiry from a student, but didn't provide any details. "We recognize that our adherence to federal law may create difficulties for our students from Iran and regard this as unfortunate," the statement said. "Furthermore, the exclusion of a class of students from admission directly conflicts with our institutional values and principles. However, as with any college or university, we have no choice but to institute policies and procedure to ensure that we are in full compliance with all applicable laws."

"I think there is a reasonable risk that these students will look at this unfortunate set of affairs and conclude that UMass Amherst is not a welcoming place for Iranian nationals to go"

In response to the criticism, the school has asked the State Department for "clarification on the whole issue," a spokesman, Daniel Fitzgibbons, said Tuesday. He left open the possibility of a loosening of the ban. "I guess it's within the realm of possibility that based on what the State Department says we may change our positiion in some way, but that remains to be seen."

Meanwhile, Iranian student groups are trying to communicate their concerns directly with the university administration, Hakim said. They are also consulting a student legal service for a possible challenge.

At stake, Hakim said, is the future of what has been a "beautiful" tradition of academic exchange between two countries.

“Institutions that provide opportunities for Iranian students to come study here help cultural diplomacy between two countries that don’t have the strongest political ties," Hakim said. "It’d be so sad to see it end at UMass Amherst."

— with Abigail Williams