This is a standard (!) question raised at some time or another by most, if not all, translators working in the field of international standardisation.

You haven’t said whether this text is intended for inclusion in an international standard, or merely refers to such a standard. And you haven’t told us which standard organisation it relates to.

With that in mind, IF the standards organisation is CENELEC, ETSI (the major European organisations involved in the standardisation of electrical, electronic and telecoms systems), then the CEN/CENELEC “PME Rules” apply. These rules are published in: CEN/CENELEC Internal regulations – Part 3, Rules for the structure and drafting of European Standards (PNE-Rules), 2009.

There is a section in these rules which establishes how words like “shall”, “may” etc. are to be used, to ensure consistency across all contributors to, and users of, standards.

For prescriptive requirements (things that are obligatory), “shall” is used instead of “must”.

For optional features, “may” is used instead of “can”.

The corresponding negatives are “shall not” and “may not”.

In my experience (which is not very recent...), similar phraseology is also imposed in other world regions, and in the relevant global bodies: ISO, IEC, ITU, etc. For consistency, the rules are also applied in most national standardisation organisations forming the membership of the regional and global bodies (eg, in Europe: BSI (UK), AFNOR (FR), DIN (DE), etc.) Most major equipment manufacturers also apply the rules - if only by contaigion or force of habit.

Note also that the “PNE Rules” are available also in French and German (and maybe some other languages now), with corresponding requirements in those languages (where applicable).

Finally, for those who are bothered that the language sometimes ends up sounding unnatural (legalistic, even), let's remember that international standards ARE legal documents.