So if you owe money to some federal entity or a state entity, they can skip the line and garnish your wages, but if it's just some collections agency, they would have to sue you first, and only with a court order could they garnish your wages.

The IRS withholds taxes from your paystub based on your W2. You can technically zero out your withholdings from the IRS, but this can incur penalties and it exposes your employer to annoying audit requests, so its discouraged at the HR level.

Paycheck withholds that come through a court order are something different entirely. And you'd really need to sit down with an actual Employment Law expert to get the fine details, as they can vary by state and county as well as by how you get paid (salary versus contractor, etc). Which agent actually gets to deduct money from your paystub, how it is escrowed, when the collector can access the money, how that deducts from your total debts, etc isn't federalized.

But I can say with some degree of confidence that unless you owe money to the IRS, the IRS isn't involved.