Gender-neutral language is a big topic. I’m just thinking of a couple of points here.

One client wants to use the masculine to include the feminine. This applies to the German original, using Student to include Studentin, for example. This problem doesn’t arise in the English translation, though. What if there is an explanation at the beginning of a long document that the masculine will be used to include the feminine, and yet there are only three places where this happens in the English translation, and those could be elegantly amended to be non-sexist – and what’s more, it might be expected for the English to be non-sexist? Of course, that’s assuming the translation is intended for an Anglo-Saxon audience.

Second point is the suggestion of following the style guidelines at Kent Law.

The key rule of thumb is to avoid using gender-specific language; resort to alternatives like “he or she” only if there is no way to write the sentence without the pronouns. In most cases, one can rewrite any sentence to avoid the need for gender-based pronouns. There are three methods explained below. The first of the three is the most desirable. Do not use “their” as an alternative to his or her; “their” should be used only when referring to a plural subject. Each of the rules here offers a method of avoiding gender-based language.

1. Rewrite the sentence to avoid the need for any pronoun at all. One can often substitute the words “the” or “a” for the pronoun.

Incorrect: A good judge takes their job very seriously.

Undesirable:A good judge takes his or her job very seriously.

Better: A good judge takes the job very seriously

I agree that one might try to avoid their as a singular, because it is unpopular with many. As a translator, I tend to compromise if the client has a particular opinion on usage. But I am unhappy with the suggestion that their is actually wrong. I was going to ask if anyone knows how old this document is, but I see now that it is version 1.1 for a law class in 1994. I haven’t got my books with me, so I don’t know what the newest recommendations for legal English might be.

Christopher Williams, in a longer article which I haven’t got (but would like to have – but now, thanks to a kind reader, I have) says that the masculine rule was introduced by Bentham and was preceded by different usage:

According to Petersson (1998: 103), the masculine rule first appeared in British legislation in 1827, partly thanks to the influence of writers such as Jeremy Bentham who advocated letting ‘the masculine singular comprehend both genders and numbers’ so as to avoid the ‘evil of longwindedness’ (cited in Petersson, 1998: 102).3 This policy ended almost 300 years of using female terms to represent women in legislative texts, a policy which emerged during the Elizabethan period, at least in the field of vagrancy legislation (Petersson, 1998: 96).

Footnote: notes from the Canadian Department of Justice:

The need to deal equally with men and women highlights the desirability of drafting using gender-neutral language. Laws that exclude references to the female gender do not promote gender equality. For this reason, gender-specific language should not be used in legislation. Gender-specific words should be replaced with gender-neutral words that have the same meaning. In addition, the following writing techniques should be considered to avoid using a gender-specific pronoun:

use the singular “they” and its other grammatical forms (“them”, “themselves” and “their”) to refer to indefinite pronouns and singular nouns;
replace the masculine pronoun with an article;
use both pronouns “he” and “she”;
use the plural;
use a neutral word or phrase such as “person”, “any person”, “every person” or “no person”;
repeat the noun;
rewrite the sentence in order to eliminate the pronoun completely.

LATER NOTE: See also Charlie Bavington’s detailed discussion of how to handle gender when translating from French to English (though applicable to other language combinations).