Potentially getting laid off – can my employer garnish my wages if I owe money on a “lay away”?

This post is actually not about me. My partner works in a bike shop and he has a lay away account with money owed. His boss has advised him he has to pay it off ASAP before he lays him off in January or he will garnish it from his wages. Can he do this? Is this legal? Thank you in advance.