That’s not entirely true - the Treasury does, in fact, call some bonds. They’ve called 30-year paper they wrote with VERY nice yields back in the early 80’s:
http://www.treasurydirect.gov/news/pressroom/pressroom_comcall011509.htm
Good point Dave. They can issue callable bonds. I do not believe they are issuing those now, though. They only issue those when there is a chance to refinance them into lower rates.
No chance of that in the future. IMHO