SAN ANTONIO -- Austin is joining San Antonio's lawsuit against the state, Gov. Greg Abbott and Attorney General Ken Paxton over Senate Bill 4, the pending law that seeks to ban 'Sanctuary Cities' in Texas.

SB4 takes effect Sept. 1.

The law seeks to punish local governments and law enforcement that don't fully enforce federal immigration law.

MORE | Austin Complaint in Intervention

Both cities say the new law will make their cities less safe by discouraging crime victims who are undocumented from reporting to police. The lawsuit claims SB4 also ties the hands of police chiefs from being able to shift resources around the city to address crimes.

"There is another section of the law that says that our police department and our police officers can't have any policy keeping them from helping ICE," said Austin's District 4 City Council Member Greg Casar.

Plaintiffs believe the law violates several Constitutional rights, including free speech and due process. City leaders will be banned from speaking against SB4 or setting policies counter to the pending law.

"An elected official such as myself could be removed from office for endorsing a policy that is contrary to Senate Bill 4," Austin Mayor Steve Adler said. 

San Antonio District 4 Councilman Rey Saldaña led the charge to get the Alamo City involved in the SB4 court challenge. He said the people he represents encouraged the lawsuit.

MORE | Original Lawsuit Filed by San Antonio

"It's mostly about politics, and it's the politics of fear," he said. "The state and their leadership are interested in politics. We reject that completely. This is about people. My constituents have told me that we don't need to live in a community where some parts of our community are afraid to approach SAPD or are afraid to report crimes."

San Antonio officials said they are not spending a dime on the lawsuit. Instead, they are supporting the efforts of MALDEF, the Mexican American Legal Defense and Education Fund. The Austin City Council has not decided if it will spend taxpayer money on the lawsuit. However, an assistant city attorney is listed as the city's representative in its filing.

No hearing's been set on the case. It has been assigned to a federal judge in San Antonio.