"Fiat justitia, ruat caelum" is often rendered as "May justice be done though heaven falls/may fall".
While I have no problem with the translation of "Fiat justitia", I do not recognise why one can render "ruat caelum" as "though heaven falls/may fall". As far, as I am aware one would need a "cum" to make a concessive statement with the conjunctive, i.e. to me it would make sense to render "cum ruat caelum" as "though heaven falls/may fall" but not merely "ruat caelum".
Can anybody explain what is going on here? Is this an ellipsis and "cum" has been dropped in it, is this a more "liberal/poetic" translation, or have I simply forgotten a function of the conjunctive that allows this translation?
Gratias ago in praeceptione!