Human-rights activists hope the new law will help find about 400 people stolen as babies, many from women who were kidnapped and gave birth inside clandestine torture centers during the 1976-83 dictatorship. Thousands of leftists disappeared over that time in what became known as the "dirty war" against political dissent.

Others see the new law as unacceptable government intrusion, legalizing the violation of a person's very identity. And as written, it could have much broader implications, enabling DNA to be sought from anyone whenever a judge determines the evidence to be "absolutely necessary."

Children of the "disappeared" were often given to military or police families considered loyal to the military government. Some have grown up not even knowing they were adopted until activists or judges announced efforts to obtain their DNA.

The project of the Grandmothers of the Plaza de Mayo, close allies of President Cristina Fernandez, was approved Wednesday by the Senate, 58-1. Since it has already passed in the lower house, it will become law once it is published in Argentina's official bulletin.

Recovering their grandchildren has been a priority for the group's members since they first began demonstrating in front of the presidential palace in 1977, carrying pictures of their disappeared relatives.

DNA technology has helped them identify 98 of 500 children who they believe were born in prison or kidnapped as infants.

Using survivors' testimony, documents from birth families, and adoption records, they have persuaded some judges to seek DNA from suspected victims of the "dirty war." But courts have sometimes ruled that a child's right to privacy outweighs a grandmother's right to know.

The new law legalizes the extraction of "minimal amounts of blood, saliva, skin, hair, or other biological samples" to determine identity. If a person refuses to provide a sample, a judge can issue a warrant for genetic material from a toothbrush, clothing, or other objects.

"It's an absolute invasion of the right to biological privacy," constitutional lawyer Gregorio Badeni said. "No one has the right to know what I have inside my body. That belongs only to me. I can give it up voluntarily, but no one can obligate me to deliver it."

Estela de Carlotto, who heads the grandmothers group, disagrees.

By allowing officials to extract DNA from personal effects, the law "doesn't violate in any way the body or the privacy," she said. "It will surely help discover the identity of the grandchildren we have been searching for for so many years."

Elisa Carrio, a leading political rival of the president, suggests another motivation: targeting Ernestina Herrera de Noble, the director of Grupo Clarin, Argentina's dominant media group and an opponent of Fernandez and her husband, a former president.

The grandmothers group believes that two babies Herrera adopted in 1976 were stolen from women who gave birth in prison before being killed.

For years, their efforts to resolve the case have been stymied because Herrera's adoptive children, now in their 30s, have refused to submit to blood or saliva tests.

The Argentine law may be unprecedented in requiring tests of people who aren't suspected of crimes, said Marcy Darnovsky, associate executive director for the Center for Genetics and Society in Berkeley, Calif.

Large forensic DNA databases in Britain and the U.S. have generated controversy because they include people arrested but not convicted or, in some cases, even charged.