They weren’t arrested for not cooperating with an ICE Detainer.
From the article, after getting beat up some deputies, it appears that the victim filed a Civil Rights complaint against the Sheriff and his deputies or filed a law suit in federal court. Sheriff and deputies made false statements to FBI, the agency that investigates Civil Rights complaints, and filed false reports. That has ABSOLUTELY NOTHING to do with acknowledging and agreeing to hold someone on an ICE detainer.
They were arrested for violating 18 USC 1001. The same charge that got Gen Flynn.
18 USC 1001 .... 18 USC 1001 - The General Federal False Statements Statute
(a) Except as otherwise provided in this section, whoever, in any matter within the jurisdiction of the executive, legislative, or judicial branch of the Government of the United States, knowingly and willfully—
(1) falsifies, conceals, or covers up by any trick, scheme, or device a material fact;
(2) makes any materially false, fictitious, or fraudulent statement or representation; or
(3) makes or uses any false writing or document knowing the same to contain any materially false, fictitious, or fraudulent statement or entry;
Anyone can be arrested for breaking the law, even the President. But, the Sheriff cannot be arrested for not helping the feds.