The Supreme Court of Canada said Thursday that the federal government will not have to pay back-interest on pensions kept in trust for thousands of mentally disabled veterans.

The seven judges were unanimous in their ruling.

The class-action lawsuit involves 25,000 to 35,000 veterans whose pensions were managed by Ottawa since the 1930s because they were judged unable to manage their own finances. Fewer than 1,000 are still alive.

Ottawa didn’t pay interest on the pensions to the veterans. When they died, the principle went to the federal government.

In 1990, the Mulroney government decided to pay the interest, but passed an amendment to the Deptartment of Veterans Affairs Act. The statute said the veterans had no right to sue for interest on the pensions prior to 1990.

In Thursday’s decision, the Supreme Court judges ruled the federal government had the right to enact the legislation.

The veterans had challenged the statute under the 1958 Canadian Bill of Rights.