Ultra posse nemo obligatur is a Latin legal term, meaning, "No one is obligated beyond what he is able to do."
Ultra posse nemo obligatur has its origin in the Roman laws which were in force for regulating civil life from the origins of Rome in 753 BCE until the final end of the Byzantine-restored western Roman Empire with the death of Justinian in 565 CE. The expression can be found in Justinian's "Digesto". The Digesto consists of 50 books, prepared at the order of Justinian, that include the sum of the works of all prior Roman jurists. The Digesto is a part of the Corpus juris civilis, which includes also the "Institutiones" and the "Codex". The term "Digesto" derives from the Latin verb "digerere" which means "to set out" , to "to place in good order", or "systematically". Digesto is also called "Pandette" which word comes from the ancient greek that means "that receives all" or "that includes all" to indicate "the completeness of the compilation". A common variant of the phrase "ultra posse nemo obligatur" is "ad inpossibilia nemo tenetur".