The Minnesota Department of Health has regained ­authority to retain blood samples from newborn babies indefinitely for public health and research purposes unless a parent refuses permission.

Gov. Mark Dayton on Tuesday signed the bill lawmakers approved last week, the latest twist in a legal battle that has pitted the medical and public-health community against medical privacy activists.

State health officials and many physicians say the tiny blood spots, typically drawn about 24 hours after a baby is born, allow early detection of dozens of hereditary illnesses and then quick treatment. Once stored by the state Health Department, the large collection of blood samples helps ­scientists study pediatric diseases.

The department was sued by a group of parents concerned about privacy of their children's medical data and challenged by the Citizens' Council for Health Freedom, which said the newborn screening system gave the state unsettling power to store and use babies' genetic information.

The new law effectively reverses a 2011 Minnesota Supreme Court order requiring the Health Department to destroy blood samples that test negative for disease after 71 days and samples that test positive after two years, unless parents "opt in" and give written consent that it can keep them. Now the state can retain the samples unless parents opt out.

staff and wire reports