In U.S. legal practice you will also find Roman numbering (i.e. Article I, Article II). If you decide to number articles in Roman numbers, you should revert to Arabic numbering for references to sections (i.e. section 2.3 would be the third section of Article II).

Article numbering. Typically, articles are given Arabic numbers with or without a full stop (1., 2., 3. or 1, 2, 3). In U.S. legal practice you will also find Roman numbering (i.e. Article I, Article II).

The rules for traditional outlining call for outlines to begin with Roman numerals (I, II, III) and to proceed through letters (A, B, C, and a, b, c) and Arabic numerals (1, 2, 3). If you supplement those levels with Romanettes (i, ii, iii), and parentheses ((a), (b), (c) and (1), (2), (3)), you can create an outline with 7 levels: I. A. 1.

Tra­di­tion­ally, hi­er­ar­chi­cal head­ings in le­gal doc­u­ments start with ro­man nu­mer­als at the top level (I, II, III); then switch to cap­i­tal let­ters (A, B, C); then nu­mer­als (1, 2, 3); then low­er­case let­ters (a, b, c); then ro­manettes (i, ii, iii); and then vari­a­tions of the above us­ing two paren ...

A classic example of the sentimental approach is the use of Articles and Sections in US contracts, often with the Article numbers written in Roman numerals and the Section numbers in Arabic numerals. By contrast, the UK approach is to have a single category – Clauses – using Arabic numerals throughout.