With Ontario about to open up adoption records dating back more than 80 years, only a small fraction of birth parents and adult adoptees have taken steps to prevent a future reunion.

By the end of April, 2,500 people – a number almost equally split between parents and offspring – had signed disclosure vetoes that would keep their identities secret when the new legislation comes into effect on June 1.

The law will give both sides of an adoption equal access to birth information for the 250,000 adoptions registered in the province since 1921.

Previously, the system was set up so that biological parents could register with the province that they were willing to be contacted, while only adult adoptees over the age of 18 were given access to birth documents to initiate a reunion.

But over the years, there has been growing pressure to make adoptions more open, particularly to help adopted adults fill in their medical histories.

The Ontario legislation follows similar steps taken by four other provinces to open up adoptions – British Columbia, Alberta, Manitoba, and Newfoundland and Labrador.

The disclosure veto was added to the legislation in 2007, after the Ontario Superior Court ruled that retroactively allowing access to confidential adoption records was unconstitutional. The new law also includes a no-contact order, which allows information to be released but carries a steep fine if contact is made against a person's wishes, and a provision allowing people to say how they wish to be contacted.

As of last month, nearly 1,100 people had requested not to be contacted at all, and more than 1,500 people had attached conditions to a reunion – suggesting, for example, that they be approached by e-mail only or through a third party.

The provincial minister of Community and Social Madeleine Meilleur said Monday that the low number of vetoes suggest that most people involved in an adoption want the option of a reunion. “It tells us we have done the right thing,” she says. “There will be, I hope, many happy people in Ontario and elsewhere [who] will find their birth mother, and perhaps birth father too, and parents will find their son or daughter.”

While the new law is “a major step forward,” Michael Grand, a psychology professor at the University of Guelph and an expert in adoption, also points to its shortcomings. For instance, he said, the government will no longer offer assistance in finding people who may have moved or changed their names, which may make it harder for adoptees and birth parents without money or expertise to conduct searches on their own with information that is often vague or out of date.

The new law also neglected to include a requirement that people requesting vetoes must still leave key medical information with the ministry, Prof. Grand said. He also believes the government should have made it possible for adopted parents to conduct a search on behalf of minor children, if they felt it was in their child's best interest.