Lex Scripta Si Cesset

ID CUSTODI. ri oportet quod moribus et consuetudlne Inductum est; et, si qua in re lioc defecerit, tunc id quod proximum et consequens el est; et, si id non appareat, tunc Jus quo urbs Romana utitur servari oportet. If the written law be silent, that which is drawn from manners and custom ought to be observed; and, if that is in any manner defective, then that which is next and analogous to it; and, if that does not appear, then the law which Rome uses should be followed.

7 Coke, 19.

This maxim of Lord Coke is so far followed at the present day that, in cases where there is no precedent of the English courts, the civil law is always heard with respect, and often, though not necessarily, followed.

Wharton.