If upheld, McAuliffe’s order could help tip Virginia, a swing state where the vote is traditionally close in presidential elections, in favor of Democratic White House candidate Hillary Clinton.
Democrat Barack Obama won Virginia in 2012 by about 150,000 votes and in 2008 by about 235,000 votes. Almost 12,000 felons have registered to vote under McAuliffe’s order, the state elections board said.
The high court is scheduled to hear arguments in a special session starting at 9 a.m. ET (1300 GMT). The plaintiffs in the lawsuit, led by leaders of the Republican-controlled state legislature, contend that McAuliffe’s April 22 order is unconstitutional since it is a blanket restoration of voting rights to felons.
The suit asks the justices to block McAuliffe’s order, which also allows felons to serve on juries and hold public office.
Before the order, felons had to petition the governor individually to restore their voting rights. Virginia is one of four states whose constitution permanently disenfranchises felons but allows the governor to restore voting rights, according to the Brennan Center for Justice, a non-partisan civil liberties group.
McAuliffe and other Democrats have hailed the restoration of rights to felons who have served their sentences and completed probation as being long overdue.
Many of the convicts benefiting from the order are African-Americans or Latinos, two groups that have voted overwhelmingly for Democratic candidates in the past.
The McAuliffe administration has refused to release the names of the felons whose rights have been restored, saying it qualifies as an executive working paper.
But last week the Virginia Freedom of Information Advisory Council issued an opinion saying the list of felons does not qualify under that exemption. The council’s opinion is not binding and cannot compel the governor to release the names.
The McAuliffe administration has acknowledged errors in compiling the list.
The Sentencing Project, a prison reform advocacy group, has said that about two dozen states over the past two decades have eased restrictions on voting by felons.