Five major cities in states across the country are suing the Trump administration over the “unlawful” freezing of federal funds that are supposed to help shield metropolitan areas from terrorist and nuclear attacks, saying the government has “unconstitutionally usurped Congress’s authority” and “violated the Constitution’s separation of powers” by withholding millions from them.

“DHS’s funding freeze is … already impairing plaintiffs’ ability to protect public safety,” the cities allege in an amended complaint filed Monday in Illinois, where lawyers for the city of Chicago sparked the legal fight last month after the Department of Homeland Security announced its funding pause on May 14.

Attorneys for San Francisco, Denver, Boston and Seattle joined forces with the Windy City this week — claiming their cities are also suffering from similar public safety issues and concerns related to the freeze, at a time when they say it’s needed most.

“On information and belief, DHS’s inaction is part of a programmatic freeze of Securing the Cities funding,” the complaint charges. “Plaintiffs have told vendors to stop work on vital equipment and have canceled training designed to protect against terrorist attacks.”

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The cities allege that Trump has cut off “Securing the Cities” program funds that have been used to buy “equipment designed to detect nuclear and other radiological materials that could be used to commit terrorist attacks” and train employees how to use it.

They employ “equipment and personnel” funded by the program to conduct security sweeps at athletic events, concerts, parades, political rallies, and other major events, according to the complaint, including rallies held by Donald Trump when he was a presidential candidate, the upcoming 2026 Super Bowl in San Francisco, and FIFA World Cup 26 matches in Boston, San Francisco, and Seattle.

“All that changed in recent months,” the new complaint says. “Since February 21, 2025, plaintiffs have submitted 11 requests to reimburse plaintiffs for expenditures that DHS had already approved,” it alleges. “DHS has effectively ignored plaintiffs’ requests while holding open the possibility that DHS may someday reimburse plaintiffs.”

The cities say federal employees have offered up responses and explanations for why the funding inquiries are being ignored. One government worker allegedly told San Francisco there was a “pause” on disbursements and said, “I have no information on when you can expect the payment,” according to the complaint.

The amended filing notes how between 2012 and 2017, the Domestic Nuclear Detection Office added the cities of Chicago, Houston, Los Angeles, and Washington, D.C., regions to Securing the Cities because the office had deemed them to be “high-risk” areas. Boston, Denver, San Francisco and Seattle were later added.

In 2018, Congress passed the Countering Weapons of Mass Destruction Act, which required DHS to “establish” Securing the Cities funding for those cities and several others “to enhance the ability” of the United States to detect and prevent terrorist attacks and other “high-consequence events.”