New Mexico is now among 21 states being sued by the Department of Justice for offering in-state tuition to undocumented students.

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The Department of Justice on Thursday policies challenged that allow undocumented students to pay in-state tuition in four more states: Arizona, New Mexico, Oregon and Washington. The agency has now sued 21 states for allowing undocumented students to pay in-state tuition.

In a news release, the agency said that by granting in-state tuition rates to undocumented students, states unfairly disadvantage U.S. citizen students from other states and incentivize unauthorized immigration. Assistant Attorney General Brett A. Shumate of the Justice Department’s Civil Division said the practice results in U.S. citizen students “being treated like second-class citizens in their own country.”

The Mexican American Legal Defense and Educational Fund plans to intervene in the four new lawsuits, according to a statement from Thomas A. Saenz, who serves as the organization’s president and general counsel. He said the latest cases are a demonstration of “the Trump administration’s misuse of the court system to continue a concerted campaign of hostility toward all immigrants.”