Oregon Gov. Kate Brown signed legislation Monday making Oregon the first state to have automatic voter registration, potentially adding 300,000 new voters to state rolls.

The “motor voter” legislation will use state Department of Motor Vehicles data to automatically register eligible voters whose information is contained in the DMV system, with a 21-day opt-out period for those who wish to be taken off the registry.

"It just changes expectations for who's responsible for making elections work," said Barry Burden, a professor of political science at the University of Wisconsin in Madison and the director of the Elections Research Center. "In every other state, it's the responsibility for the voters to make sure it happens."

Supporters say the legislation's goal is to keep young voters, students and working families who move often from losing their right to vote. Republican lawmakers, who unanimously voted against the bill, complain it puts Oregonians' privacy at risk.

Under the state law, the Oregon secretary of state will use the DMV data, which includes information on whether a person is a citizen, to register voters, who would then be sent a postcard with information on how to opt out of registration.

"A one-size-fits-all approach to voter registration does not work for our most vulnerable citizens that could be endangered if their personal information is suddenly made public," Republican state Sen. Kim Thatcher said in a statement.

According to The Oregonian, the Democratic House majority leader, Val Hoyle, said that police officers, domestic abuse victims and others who are already allowed to keep their DMV information private will not have their data transferred to the voter rolls.

State Sen. Elizabeth Steiner Hayward, a Portland Democrat who carried the bill in the Senate, said there were rumblings the measure was a secret plot to enroll more Democrats. But she denied that was true.

Oregon already has one of the highest voter registration rates in the nation; during the 2014 general election, 73 percent of Oregonians were registered to vote, and 70 percent of them cast ballots.

The law comes at a time when many other states are putting more of the onus on citizens to prove their voter eligibility. Since the 2010 midterm elections, 22 states have approved legislation tightening voter restrictions, according to a report from the Brennan Center for Justice. Thirteen of those states passed voter ID laws, requiring citizens to provide identification to prove they are eligible to vote.

Proponents of such legislation say it is necessary to prevent voter fraud. But rights activists have criticized the legislation, saying that it creates barriers to entry for poorer citizens, young voters and people of color, all of whom are less likely to have the required forms of identification.

Last Thursday, Rep. John Lewis, D-Ga., referred to voter ID laws as "poll taxes by another name," a reference to segregation-era laws that were intended to prevent black people from voting.

Al Jazeera and wire services