When Nicole Noblet’s parents told her they planned to move the family to Missouri to retire, she worried that the move from Minnesota could affect her rights. So she did some research.

What she learned dismayed her: Because of the voluntary guardianship she had entered into with her parents, Noblet, now 32, wouldn’t be allowed to cast a ballot in her new state.

She told her parents she wanted to revisit their legal arrangement, a common one for people with disabilities that allows them to make health care and financial decisions for her. “I said, ‘Nobody is going to take away my right to vote.’ ”

Missouri is one of at least seven states, according to the Bazelon Center for Mental Health Law, that say anyone under a guardianship agreement cannot cast a ballot unless a judge decides otherwise.

Guardianships, and similar arrangements called conservatorships in some states, give a court-approved guardian, who might be a parent, a caretaker or even a public defender, decision-making authority over a person. It may be limited to certain matters, like financial or health care decisions, or it could extend to every facet of the person’s life.

Many of the state laws are decades or even centuries old, and presume that anyone under guardianship is mentally incompetent. Some laws continue to refer to them using outdated and demeaning terms like “idiot,” “lunatic” and “retarded.”

The Justice Department said this year that such blanket policies are illegal under federal civil rights laws. But the Biden administration appears to have taken no action to enforce that view.

Some people under guardianship, like Noblet, have gone to court to get their rights restored, which can be a long and difficult process. Others have challenged or sought changes in state laws. In 2001, a federal judge overturned a prohibition in Maine on voting by people under guardianship.

In the latest case, an Arizona court ruled in May that the state could not automatically deny voting rights to people under guardianship without proving that they are incompetent.

The National Council on Disability estimated in 2018 that about 1.3 million Americans were under guardianship arrangements, and studies suggest that the number has been growing rapidly, more than tripling over the past three decades. They include older Americans who can no longer manage their affairs, but also many younger people, including some with intellectual or developmental disabilities.

Advocates for people with disabilities say guardianships of all kinds have sometimes been used too broadly to deny basic rights.

Most states restrict the voting rights of those in such agreements. And under federal law, people under guardianship are one of only two groups that can routinely be denied the right to vote; the other is people with felony convictions. In addition to the seven states that flatly prohibit anyone under guardianship from casting a ballot, more than two dozen other states have restrictions that vary by the type of guardianship or level of disability, and often require a judge to decide case by case on the right to vote.

Michelle Bishop, who works on voting accessibility issues for the National Disability Rights Network, said the effect is to hold people with disabilities to a higher standard than other voters.

“They somehow have to prove that they understand how our government works, what elections mean, and they have to have a good reason for voting for who they want to vote for,” she said. “There are a lot of nondisabled Americans who can’t do any of that.”

The Justice Department’s guidance to state officials, issued in April, says explicitly that under the U.S. Constitution and federal law, including the Americans With Disabilities Act, states can’t deny anyone the right to vote simply because of a guardianship arrangement.

The department also said that the use of competency tests to determine whether people with mental disabilities are allowed to vote is illegal. Voting rights advocates have compared them to the literacy tests used to disenfranchise Black Americans in the Jim Crow era.

Some experts argue that there are valid reasons to limit the voting rights of people under guardianship, or to require them to prove competency before going to the polls. Dr. Paul Appelbaum, director of the division of law, ethics and psychiatry at Columbia University, suggested a minimum competency standard would not be unreasonable.

“My concern is more with the participation of people who may simply not really understand what it is that they’re doing,” he said.

Proponents of the restrictions say people with cognitive impairment may be susceptible to having their votes influenced by caretakers or cast fraudulently by others in their name, though there is no evidence of widespread problems.

Missouri, where Noblet and her parents moved in 2021, has been among the most aggressive states in removing people deemed mentally incompetent from the voting roles, according to an analysis by public radio organizations. Between 2008 and 2016, more than 10,000 voters were purged in Missouri because they were deemed mentally incompetent, the news organizations found — more than twice as many as any other state during that time period.

The secretary of state’s office in Missouri did not respond to requests for comment about the state’s voting policies.

It took Noblet, even with the support of her parents, more than a year to persuade a Minnesota judge to dissolve her guardianship so that she could vote in Missouri. But she was determined.

Noblet is autistic and experienced a traumatic brain injury when she was 25. She uses a wheelchair to get around and a speech-generating device to communicate. She is especially eager to back candidates who will ensure that she retains access to reproductive care, including contraceptives. “Birth control is something that I use to stay healthy,” she said.

Noblet said she would always push for people with disabilities to have the opportunity to participate in elections.

And when Missouri held a primary this month, she helped ensure it by serving as an election judge at her local polling place.