The committee allowed van der Vorst to keep her medals, ruling that she had not deliberately misled them. But later it emerged that perhaps she had. Reports surfaced in which even van der Vorst said there had been times when she could stand and walk while competing as a Paralympian.

“What would be the reaction of competitors who had raced Victoria if, in a few years, she was able to walk?” Van de Vliet said.

The committee often reclassifies athletes and places them into different competition classes, depending on the severity of their impairments. It has declared athletes ineligible before, including some who have simply misinterpreted the rules. Recently, Van de Vliet said, a Jamaican competitor showed up at a competition with a note from his optician saying “this man has a visual impairment, but when he wears his glasses, everything’s fine.”

The committee sent him home. Van de Vliet said, “It was a particularly sad case.”

Arlen’s situation is different, in part because she is such a high-profile athlete. After the International Paralympic Committee ruled her ineligible, her case became a cause célèbre, with sympathetic reports on “Good Morning America” and other outlets. New Hampshire’s governor and two senators publicly criticized the committee’s ruling.

Photogenic, poised, articulate, bitterly disappointed, a television natural (she also models and works as a motivational speaker), Arlen makes a formidable opponent for the Paralympic committee. It is impossible to hear her story — about being a star child athlete who suddenly grew weaker and weaker and sicker and sicker until she became incapacitated; about her years in a vegetative state and her family’s search for medical answers; about how she woke and had to relearn to talk, read and eat; about how she resolved to be a Paralympic swimmer; about her triumph last summer — without feeling sympathetic.

“She was brought into the Paralympic movement by people who knew about it and told her she could be good at it, and she trained and did everything she was asked to do,” Arlen’s coach, John Ogden, said in an interview. “She has been emotionally scarred and traumatized by this. I am so disappointed in the Paralympic movement right now, I can’t even tell you.”