A cease and desist letter filed Wednesday alleged that the Garfield County sheriff intentionally violated state law by collaborating with the U.S. Immigration and Customs Enforcement (ICE).

The letter, filed by the law firm Towards Justice, claimed that Garfield County Sheriff Lou Vallario told other law enforcement officials that he would not comply with Colorado’s limitations on law enforcement’s ability to work with ICE while a legislative proposal was being drafted.

Since the bill’s passing, the sheriff followed through with action, the letter alleged.

“I will not comply with this, if this draft is the end result. You can call me ‘defendant’ in a lawsuit to correct this pro-criminal stupidity,” Vallario wrote in an email, according to records obtained through the Colorado Open Records Act and provided in the letter.

The letter is the latest effort to reprimand a local law enforcement agency for allegedly sharing information with federal authorities, which then used the data to detain individuals illegally staying in the U.S.

Last July, Colorado Attorney General Phil Weiser sued a deputy of the Mesa County Sheriff’s Office after the officer allegedly shared information about a college student who had overstayed her visa via a multi-agency communications channel that included federal agents. Weiser’s office ultimately dropped the suit after the deputy resigned.

David Seligman, a candidate for attorney general in November, is the executive director of the firm that filed Wednesday’s cease and desist letter.

The letter alleged that through the creation of the Special Problems Enforcement and Response (SPEAR) task force — which pools data, resources and information across different law enforcement agencies, including federal authorities — Vallario deliberately violated a Colorado statute that prohibits certain information from being shared.

There is no record of any municipal government authorizing the agreement, the letter says, adding that the lack of such an arrangement suggests a “deliberate effort” to cooperate with federal immigration authorities outside the public’s purview.

“Sheriff Vallario and other law enforcement across the state seeking to collaborate with ICE must know that they are not above the law,” Seligman said in a news release.

A spokesperson with the sheriff’s office said Friday that officials had not yet seen the letter and any claims would have to be reviewed by the Garfield County District Attorney’s Office.

The letter from Towards Justice outlined ICE’s detainment of Luis Armando Rivas Martinez on June 3, 2025, allegedly with the collaboration of the sheriff’s office and SPEAR. Rivas, described as “a longtime Garfield County resident,” was detained for “immigration and customs violations” and placed in the ICE Processing Center in Aurora for three months before he was deported from the country, the letter alleged.

The sheriff’s office also illegally coordinated jail releases with ICE, providing federal agents with non-public information on individuals and releasing them upon ICE’s request — without a judicial warrant, according to the letter.

The state’s leaders, including Gov. Jared Polis, have insisted that Colorado is not a “sanctuary state,” defined as jurisdictions that prohibit cooperation between state and federal authorities on immigration enforcement.

Polis, in a January response to the U.S. Drug Enforcement Agency saying that it has been difficult to operate in Colorado given its current immigration enforcement laws, said local law enforcement can, and should, work with federal drug enforcement officers when it relates to drug activity.

Reporter Marianne Goodland contributed to this article.