Not strictly a
Roman Law phrase, but this
Latin sentence is often used to describe the situation of a constituion in a war conflict. Directly translated it means 'while war, law is silent'. Sometimes, the goverment have to suspend some of the functions of the law system in order to conduct military operations effectively and safely. One of the most serious downsides to this is the restriction of the
freedom of speech. Countries such as
India has a clause the suspends some of the normal constitution when in war. Roman law-centered countries such as the US have the emergency war-laws in the ordinary law book.
A good example of this is the transfer of power from the Norwegian Storting to the excecutive branch after the German attack on Norway april 9th 1940. The goverment was handed full power (By the Storting, it was voted upon, noone voted 'nay'.) to run the country while the Storting was out of function or unable to vote on laws under German occupation. The goverment, which is formally lead by the King, fled to England and coordinated the resistance from there. The constitution in Norway was set aside and a "inter arma silent leges" situation was in effect.