San Antonio, TX – Texas counties that challenge the eligibility of voters simply because they were not U.S. citizens in the past run the risk of lawsuits under the U.S. Constitution and federal laws, according to a letter sent Monday by civil rights attorneys.

MALDEF (Mexican American Legal Defense and Educational Fund) sent the letter in response to a claim issued last Friday by the Texas Secretary of State that thousands of ineligible voters may have cast ballots in previous elections.

Texas officials compiled their list of suspect voters based on information provided by the Texas Department of Public Safety about individuals who were non-citizens at the time they applied for a driver’s license or state identification. That information, however, does not indicate whether individuals obtained citizenship after applying for a driver’s license.

“The Texas Secretary of State has launched a purge effort against tens of thousands of voters he knows are naturalized citizens,” said Nina Perales, vice president of litigation at MALDEF. “Targeting naturalized citizens for voter purges is unconstitutional and will do lasting damage to the Texas electorate.”

In the letter, MALDEF notes that “the fact that a permanent resident immigrant lawfully obtains a driver’s license in Texas, and later naturalizes, should not cause you to scrutinize that voter’s eligibility any more than the eligibility of a native-born U.S. citizen.”

The state’s claim of illegal voting follows numerous studies that have found no evidence of large-scale voter fraud in the U.S.

Read the letter here.