The phenomenon of multilingual law stems from official multilingualism, which usually requires not only that the law should be enacted in all official languages, but also that texts of a single legal instrument expressed in different official languages be treated as equally authentic. Since all authentic language versions are equal, all of them should be taken into consideration and none of them should prevail for interpretation purposes. In order to guarantee this equality, the principle of equal authenticity presumes that all authentic language versions are originals and render the same meaning. However, in practice, multilingual law is often drafted by means of translation. Hence, there is a risk that those language versions prepared by means of translation will be deemed of questionable reliability, and therefore will not be considered when a multilingual legal instrument is interpreted. Contradictions between the presumptions behind the principle of equal authenticity and practice of multilingual legislative drafting draw attention to a paradox which can and has challenged the equality between authentic language versions. The thesis provides strong evidence - through a comparative study of multilingual legislative drafting in the European Union and Canada - that legal presumptions established by the principle of equal authenticity and the practice of legal multilingualism are more congruent than may appear at first glance. In particular, the study reveals that the equality between authentic language versions results not only from legal presumptions and provisions but can also be assured in practice throughout the drafting process. This is evident in the bilingual codrafting process currently applied in Canada at the federal level. But it is also discernible in EU multilingual legislative drafting methods, which combine elements of translation and codrafting. The detailed examination of legal drafting within EU institutions demonstrates that all languages participate in all drafting stages and influence each other. Therefore, although some elements of translation are involved in the drafting of EU multilingual law, by the end of the drafting process none of the language versions can be identified as a pure original, thus guaranteeing that the equality of all language versions is preserved.