More than 30 Democratic mayors plan to file an amicus brief in support of President Barack Obama's efforts to shield more than 5 million undocumented immigrants from deportation in an ongoing legal battle to overturn the White House policy. New York City Mayor Bill de Blasio announced the legal wrangling aimed at rallying behind Obama's immigration policies on Friday. 

The amicus brief opposes a lawsuit filed in Texas by Republican governors who claim Obama's executive action on immigration announced in November is illegal because the measure was not approved by the GOP-controlled Congress. The National League of Cities and U.S. Conference of Mayors, as well as Democratic leaders including Los Angeles Mayor Eric Garcetti, San Francisco Mayor Ed Lee and Chicago Mayor Rahm Emanuel claim Obama's immigration measures serve public interests across the nation. 

The lawsuit representing more than 25 states led by Republican governors was filed in the Federal District Court for the Southern District of Texas. The states argue that "unilateral suspension of the nation's immigration laws is unlawful" and that only the court's "immediate intervention can protect the [states] from dramatic and irreparable injuries." The states involved include: Texas, Alabama, Arizona, Arkansas, Florida, Georgia, Nebraska, North Carolina, North Dakota, Ohio, Oklahoma, South Carolina, South Dakota, Tennessee, Utah, West Virginia and Wisconsin.

“Delaying implementation of the president’s executive action will further hurt our families, negatively impact our economies, and create unnecessary insecurity in our communities,” said de Blasio in a statement. “We are organized, and we will fight for the changes this nation needs and deserves, and fight those who oppose immigration reform, be it in the courtroom, in Congress, or in our communities."

The legal filing came after de Blasio hosted a summit of Democratic city officials in December in New York City aimed at brainstorming ways to persuade high numbers of immigrants living in the United States without legal status to apply for protection under Obama's delayed deportation policy. Obama's immigration reform measure would extend legal rights, including work visas, to illegal immigrants who met certain requirements, such as having children who are U.S. citizens.