I must say that I don't know how to proceed here, if it is, like goncin said, "Uma das máximas do Direito Romano", maybe this "devemos/debemus" is implied in the Latin version (as one of the precepts of right in the Roman law -that were to be respected, and definitively issued as it is in the original version, probably a copy-paste from it)...
This is a motto of Cato the Elder according to Cicero. Yes, the verb is default here, but maybe we should add "Debemus" in brackets like it is in goncin's translation?
Thanks for your answers! Actually, I couldn't add "debemus" to the original text, because of its size -too many characters-, so I added it in the remarks field with an explanation about an implied verb.