U.S.A.R.F.U. National Office 3595 E. Fountain Blvd. Colorado Springs, Colorado 80910 phone: 719-637-1022 fax: 719-637-1315
It's also available from major rugby suppliers.
The laws contained in the handbook are those of the International Rugby Football Board (IRFB) with instructions and notes on the laws as framed by the IRFB along with Directives and Variations on the Laws for the USARFU. The handbook also contains information about amateurism and the USARFU itself.
This one is recommended.
The USARFU office also distributes The Laws in Plain English for $6. This is a very readable publication with illustrations. I would recommend it to beginning players as more useful for them than the lawbook.
For the complete novice, there is also a little pamphlet called Instant Rugby: a 5 minute guide to the laws for about $1. It's probably worthwhile for that friend you want to drag along to watch you play.