Federal judges can deputize State and local police to enforce court orders.
You might be conflating two principles.
Under Fed. R. Civ. P. 4.1, process for civil contempt may be served "by a person specially appointed for that purpose," if not by a marshal. The service need not be accomplished by a state or local law enforcement official. In fact, the person need have no additional authority or office other than having been appointed by the court. In practical terms it simply makes sense for the court to appoint someone who is already trained to serve process, or has law enforcement training, but this is not required.
Depending on the nature of the contempt, the contemnor may be held in custody until such time as he deigns to comply with the court's order. But this is separate from the service of process. It is unclear whether the
service of process may extend to the
enforcement of an order contained therein, by a court appointee. Since we find similar language in the rules of procedure that empower "persons appointed" by the court as enforcement for other purposes (e.g., civil forfeiture), it is likely this rule can be construed to allow the server of process for civil contempt to have the court's authority also to enforce the order. It is also unclear how this would operate when the contemnor is a principal officer of the executive, since a writ of mandamus may be the more proper remedy.
You may be thinking of various instances in statute (e.g., 49 U.S.C. § 44922) in which various agencies of the federal government may deputize state and local officials to supplement their enforcement. This is not a judicial matter, and the state or local executive must volunteer their forces. Otherwise it would be disallowed under the anti-commandeering doctrine. This is the principle behind sanctuary jurisdictions (as we discussed in its own thread), and also the principle by which the Texas state police act as deputies of ICE along the Texas-Mexico border.
Except that Trump already has pardoned criminal contempt of court, to help out fellow racist Joe Arpaio.
In order to challenge that, the claimant would have to retry the argument from
Ex Parte Grossman, 267 U.S. 87 (1925) that got only slight traction in that case. The notion that contempt is not a crime against the United States (i.e., a violation of statute) but rather a violation of court authority (i.e., common law) has some roots in very old-timey law, and has been raised recently as a possible avenue for challenging pardons for criminal contempt, it remains a long shot.
