Rules of the Game for British American football can be found here.
Other core documents:
BAFA Guide to Self-Officiating for 11v11 contact
BAFA Guide to Self-Officiating for 11v 11 contact – appendix 1: game day audit
BAFA Guide to Self-Officiating for 11v 11 contact – appendix 2: game day checklist guidelines
League Republic User Guide