Tell him if he isn't caught up he can kiss his taxes good bye has well.
Federal law authorizes the pay of active, reserve, and retired members of the military and the pay of civilian employees of the Federal government to be garnished (or attached) for the payment of child and/or spousal support. The law is found at 42 U.S.C. 659, and the implementing regulation is found at 5 C.F.R. Part 581.