Here’s a look at the history of tear gas and why it remains so controversial.

The Chicago crackdown, dubbed “Operation Midway Blitz,” began in early September. Masked, armed agents in unmarked trucks patrol neighborhoods, and residents have protested in ways big and small against what they see as their city under siege.

“States, generally speaking, are not allowed to limit what federal officers do,” DePaul University law professor David Franklin said. “The federal government, federal law definitely limit what federal officers can do.”

The judge’s order came less than 24 hours after Border Patrol Chief Greg Bovino fired tear gas at a crowd during an aggressive raid in Little Village.

The incident, which took place in the heart of one of Chicago’s wealthiest and most tourist-friendly neighborhoods, marks the second straight day that federal agents have deployed tear gas against Chicagoans and the sixth time in 21 days.

If agents deployed tear gas without a warning, that would violate an order issued by U.S. District Judge Sara Ellis two weeks ago.

“Donald Trump is counting on your silence,” Gov. JB Pritzker said. “We are counting on your courage.”

“These federal agents are operating lawlessly, demonstrating utter disregard for our constitutional rights,” Ald. Mike Rodriguez (22nd Ward) said.

Ruben Torres Maldonado has been held at the Broadview ICE Facility since Saturday, according to attorney Kalman Resnick, who is representing Maldonado's family. Maldonado, who has lived in Chicago since 2003, is scheduled to have an immigration court hearing Thursday, according to Resnick.

To ascertain if county jails are complying with the state’s TRUST Act, WTTW News sent Freedom of Information Act requests to each of the 90 county jails in Illinois to obtain copies of intergovernmental agreements with the U.S. Marshals Service.

State Rep. Hoan Huynh, a candidate to represent Illinois’ 9th District in Congress, said he was in Albany Park when he was confronted by six Border Patrol agents.

U.S. District Judge Sarah Ellis said Thursday she was “not happy” that immigration agents appear to have violated her order not to use tear gas and other weapons against journalists, protesters and anyone not posing an immediate threat to immigration enforcement agents.

The gatherings are part of a mass mobilization across the U.S. and globe positioned as a denouncement of President Donald Trump and his administration’s policies. In Chicago, they come amid sustained immigration raids.

Immigrations and Customs Enforcement official Russell Hott is exiting his post in Chicago and returning to Washington, a day after a federal judge in Illinois demanded he appear in court to answer questions about his agency’s continued use of tear gas in and around the city.

On Saturday, thousands of Illinois residents will take to the streets as part of the “No Kings” protests happening nationwide. Here are the details.

“Our founders understood that freedom cannot thrive under the shadow of military control,” retired Maj. Gen. Randy Manner said. “Civilian police accountable to local leaders and bound by civil law are the right tools for maintaining order, not troops and tanks.”