Legal translation is a lot like translating restaurant menus.
Firstly, both types of translation are full of culture-specific or non-equivalent terms, i.e., terms that only exist in the source language or at least don’t exist in the target language. This presents all sorts of interesting challenges that you can’t always treat in the same way. For instance, for culinary terms like calçots, sangria and crema catalana, all culture-specific, you’d probably do something different in each case.
While it’s probably not enough just to translate calçots as some kind of stringy onion or using the correct English agricultural term to truly make restaurant goers aware of what they’ll be getting themselves in for in ordering them, you probably wouldn’t be doing anyone any favours if you translated sangría at all. Crema catalana probably sits somewhere on the borderline: you have a few different options for getting the idea across, and maybe you’d always leave the original term in there somewhere.
Either way, creativity is required, just as it is when translating non-equivalent legal terms. You just can’t always get away with using somebody else’s solutions (e.g., from a dictionary or a glossary) when translating legal documents. At some point, based on your understanding of the subject matter and the document at hand, you have to be brave enough to invent a little to get meaning across in an effective way.
Secondly, there seems to be a general idea that both legal and restaurant-menu translations are notoriously bad. I’m not sure this perception is true, although maybe to some extent it goes with the territory. Because, let’s face it, when you have to deal with lots of culture-specific terms (more the case when translating menus, which are just list of terms) there is always a greater chance for a degree of awkwardness to creep in, which, while possibly necessary for understanding, may not be easy on the reader.
However, maybe there are simply just more bad rather than good translations out there. In any case, regardless of the general standard in either of these fields, good legal and menu translations are possible and should always be the goal. So, don’t stop until you get there or get it!
Thirdly, there’s lots of regional variety and constant reinvention to deal with in both legal and menu translation. Just as each restaurant and chef has the freedom to create new dishes and rename dishes whenever they like, so too can law-making bodies reinvent regulations and what they call them whenever they feel the urge.
Fourthly, there is also the question of form. While restaurant menus may all look like just a list of foods, the local meal customs could be a factor to take into account when translating a menu. In practice, though, menus probably don’t usually look that different in terms of format (apart from maybe more photos on menus in touristy places!) or take into account differences in local eating customs.
To the contrary, they usually mould the local food to international or generic customs (at least in places where the menu must be translated), something else that you could say also happens in legal translation as legal documents often are internationalised to take into account foreign formats and legal systems.