The National ICE Council, the labor union that represents federal officials who work for U.S. Immigration and Customs Enforcement, filed a notice Monday of its intent to sue the City of Portland.

The tort claim notice says the union reserves its right to sue the city for "violations of their State and Federal Constitutional Rights."

The letter, written by lawyer Sean Riddell, alleges that Mayor Ted Wheeler wrongly ordered Portland police to stand down as a protest camp blockaded a federal building in Southwest Portland.

Protesters blocked employees' access to the building for several days, managing to temporarily shut it down in late June. Wheeler initially said Portland police would not get involved in the protest unless there were risks to peoples' lives or safety. On June 28, federal officers moved protesters back and secured a police line around the building. A spokesman for the Federal Protective Services described the protest as "very, very peaceful" at that point.

The protest camp lasted from June 17 to July 25, when Portland Police finally swept the remains of a near-empty tent city.

The ICE union has argued that police declined to respond to some calls for service and that refusing to do so violated the federal officials' civil rights. Wheeler has rejected that assertion.

Today's notice repeats that claim.

"Mr. Wheeler has an inherent obligation to not use the Portland Police Bureau to advance his own political agenda or use his police powers to harm those he believes possess alternative political beliefs," today's notice says.

A spokeswoman for Wheeler's office says the city cannot comment on pending litigation.