Texas Civil Rights Project
The Trump administration has been detaining migrant children as young as a year old in hotels, according to the lawsuit.
The groups' decision to sign on means Mason will be represented by some of the top voting rights attorneys in the country.
The Texas Civil Rights Project found that 272 families have been separated at a single Texas courthouse since June.
There are not nearly enough immigration lawyers in the Rio Grande Valley to meet the needs of a large detainee population.
Advocates describe painful conversations with parents who have been separated from their kids at the border.
President Donald Trump has ordered the separation of undocumented families as a "zero-tolerance" border policy.
Plaintiffs complained that the state violated the 1993 National Voter Registration Act.
People who tried to register to vote while renewing driver's licenses online had to print out and mail in another form.
Every year, the American Library Association declares the final week of September "Banned Books Week," commemorated in many libraries with displays designed to highlight often-overreaching censorship of school and public libraries.
The plaintiffs are four criminal defense attorneys in Travis County, the Austin Lawyers Guild and the Prison Justice League