The essay provides an overview of the formalities established by civil law, canon law and city statutes in order to draft a will in the Middle Ages. It is well known that legisti repeatedly addressed the issue posed by the foreigner who made a will in a city which had local provisions in place that derogated from the ius commune. In particular, Bartolus pointed out some conflict-of-law rules about contracts, criminal law, wills and succession. However, the implementation of these rules sometimes clashed with the jurist’s conscience. In some consilia, Baldus highlighted the doubts which would arise when compliance with the strict rules of the ius civile meant betraying the wishes of the deceased.