(Reuters) - Ten Republican state attorneys general on Thursday urged federal authorities to rescind a policy set by former U.S. President Barack Obama that protects from deportation nearly 600,000 immigrants brought into the country illegally by their parents, known as “Dreamers.” Obama, a Democrat, had hoped that overhauling the U.S. immigration system and resolving the fate of the estimated 11 million people in the country illegally would be part of his presidential legacy. But Republican President Donald Trump has vowed to crack down on illegal immigration. The Department of Homeland Security earlier this month rescinded a separate Obama-era policy meant to cover illegal immigrant parents that had been blocked by the courts. However, DHS said the Deferred Action for Childhood Arrivals, or DACA, policy covering “Dreamers” was still in effect. In a letter on Thursday, the Republican attorneys general asked that DHS abolish the DACA program going forward, while noting that the government did not have to rescind permits that had already been issued.  If the federal government does not withdraw DACA, the attorneys general said they would file a legal challenge to the program in federal court in Texas. A DHS representative referred questions to the U.S. Department of Justice, which did not immediately respond to a request for comment. The 10 Republican attorneys general who signed the letter represent the states of Texas, Louisiana, Alabama, Nebraska, Arkansas, South Carolina, Idaho, Tennessee, West Virginia and Kansas.  A larger coalition of 26 Republican AGs had challenged the policy covering illegal immigrant parents.  In a statement, the Mexican American Legal Defense and Educational Fund said it took encouragement from the diminished number of attorneys general signing onto the DACA letter, and urged Trump not to “cave in to the toothless threat” of legal action. 