Restitution is a creature of statute, specifically the Mandatory Restitution to Victims Act at 18 U.S.C.§ 3663A. The statute requires that restitution either attend the offense of conviction or an agreement of the parties, and that the offense must be the direct and proximate cause of harm to the victim. "[T]he Government must show both that the defendant’s conduct is the ‘but-for’ cause of the individual’s harm and that the defendant ‘proximately’ caused the harm."
The court often orders monthly restitution payments as a condition of supervision. In that event, other means of collection, such as garnishment, cannot be contemporaneously pursued by the government. That is double dipping, as the Tenth Circuit recognized today in US v. Martinez: "The government can enforce a restitution order only in a manner that does not exceed the payment obligations set out in the restitution order." The court had ordered Mr. Martinez to pay $2.7 million in restitution, and to pay monthly installments of 25% of net disposable income. The government could only enforce the court's order, not collect by other means at the same time.
One other point from the Martinez opinion. The court's oral pronouncement conflicted with the written judgment. The oral order controlled. "When the oral and written orders conflict, as they do here, we look to the oral pronouncement."
Restitution in child porn cases is a different matter, and infinitely more difficult to appraise. Also a creature of statute, it has been complicated by the Supreme Court decision in Paroline v. United States, which orders the district court to award restitution in an amount somewhere between a "token" and "severe." The court must disaggregate the original harm to the victim based on the defendant's offense of conviction. U.S. v. Galan, 804 F.3d 1287 (9th Cir. 2015). The Tenth Circuit has been rather demanding "regarding the specificity required to reach a proximate cause determination." U.S. v. Benoit, 713 F.3d 1 (2013) (Benoit I); U.S. v. Dunn, 777 F.3d 1171 (2015) ("But the clear rationale of Paroline is that a defendant should be held accountable for the measure of losses that he individually has caused."). And the government cannot pursue collection during the period of supervision, except to enforce the court's restitution order. No double dipping.