The Defense Department, in its first attempt under a new law to keep certain technical data from reaching enemy hands, has told scientists at a symposium this week in Arlington that they may attend certain sessions only if they sign statements certifying that they are American citizens and will not make the information public.

Foreign scientists may attend if their embassies certify that they agree to certain restrictions and if the Defense Department approves them.

In imposing the restrictions on about 25 papers -- none dealing with classified research -- the Pentagon also ruled that about a dozen others had to be canceled because, although their research was unclassified, the papers contained classified information.

The restricted and canceled papers, all based on Pentagon-sponsored research, deal largely with advanced laser technology, including methods of communicating with submarines using laser beams bounced off satellites.

A spokesman for the scientific group, the International Society of Photo-Optical Instrumentation Engineers, said it agreed to the restrictions as "an extraordinary measure, an experiment really" because the alternative would have been to cancel all the papers.

"This is a new thing. DOD Defense came along at almost the last minute and started pulling these papers after the program was all set," said Barry Johnson, chairman of the society's symposium planning committee.

Johnson said most of the affected papers were salvaged by moving them to a newly organized restricted session.

"We'll see how this arrangement works and decide later whether we want to do this again," Johnson said. "The alternative would be not to have these papers at all. We support the open flow of information but not if it endangers the security of the United States."

A Pentagon official said the restrictions were imposed under a new law, passed as part of the 1984 Defense Authorization Act. The law says the Pentagon may restrict access to any information the export of which would violate the Arms Export Control Act, a measure designed to keep advanced military technology from the Soviet Union.

Previously, according to Frank Sobieszczyk of the Pentagon's Office of Research and Advanced Technology, such information had to be released to anybody who filed a request under the Freedom of Information Act. Sobieszczyk said that foreign agents commonly acquired militarily useful information this way.

The Defense Department's extension of the new law to scientific meetings has raised concern among scientific groups. Last week three of the most prestigious ones met in closed session to consider whether and how the scientific community should respond.

"Clearly there is a problem here," said Mitchell Wallerstein of the National Academy of Sciences and the National Academy of Engineering, two of the groups. "This appears to be a continuation of the same set of issues we have faced in the past, and it is a matter of substantial concern to all the societies. Things like this tend to have a chilling effect on scientists."

Similar actions by the Pentagon,, have been taken at least 13 times since 1980 according to Rosemary Chalk of the American Association for the Advancement of Science, which met with the two academies last week.