The attorney does need a court order to garnish your pay. That would require a bit of time, but not much. If this is an experienced collection attorney, he could have that order in less than 45 days. Your employer could begin garnishing wages in less than two months from the date of this letter. This kind of judgment is good for 10 years from the date the court originally signed the order.
Upon it's ratification, the Constitution of the United States of America established the United States as a Constitutional Republic. Despite popular belief and what many people may believe, the United States is not now and never was a Democracy.
The first article of the Constitution establishes the legislative branch of the government and establishes what powers Congress may exercise.