Former Kansas Sen. Bob Dole was back on Capitol Hill this week, urging his former colleagues to ratify a United Nations treaty on the rights of people with disabilities.

The treaty is modeled after the Americans with Disabilities Act, which Dole steered through Congress when he was the Senate minority leader in 1990. Dole, who was the 1996 Republican presidential nominee, was injured in combat during World War II and never fully regained use of his right arm.

Supporters of the treaty, which has already been ratified by 143 other nations, say it would make the ADA a non-binding international standard for the rights of people with disabilities.

But it has run into opposition from conservatives in the Senate, including Republican James Inhofe of Oklahoma, who has said the treaty would infringe on U.S. national sovereignty.

This is the second time Dole has tried to push the treaty through the Senate. In December 2012, he returned to the Senate floor for the first time since retiring and sat in his wheelchair as the treaty fell five votes short of the two-thirds majority needed for ratification. Both current Kansas senators, Pat Roberts and Jerry Moran, voted against it.

Supporters of the treaty were especially upset with Moran because he had earlier endorsed its passage. Roberts, who is now running for re-election, said through a spokesperson that he “voted his conscience,” and suggested Dole would understand.

According to a recent New York Times story, among those opposing the treaty are advocates for people who home school their children. They claim it would take decision-making power away from parents of disabled children.