Regula pro lege, si deficit lex: If the law is inadequate, the maxim serves in its place.
(this one seems somewhat convoluted). . .
Rei turpis nullum mandatum est: There is no mandate for a thing immoral (or illegal). - Hence, there is no action for failing to act on such a mandate.
Printed copy · Anthology Volume 5, page 624Printed copy from The Tender For Law Anthology, Volume 5, page 624 (printed 13 June 2014). Added by this site; not part of the Facebook export.