In addition, I can present the case of France, where judges must disregard laws that contradict treaties (the hierarchy of norms being Constitution > Treaties > Laws > Executive orders). Therefore treaties, even with no national law to implement them, have a direct effects on the law.
Once a treaty enters into effect, a nation is bound by the terms of the treaty even if they do not have implementing laws. However, in many cases treaties don't have any consequences if signatories don't pass implementing laws (see, e.g, the Kyoto Protocol).
Lawyer here — very few of us know more Latin than the odd artifact such as ejusdem generis or contra proferentem, which occasionally are relevant to contract interpretation. And those of us of a certain age who grew up Catholic will remember bits and pieces of the old Latin Mass. Otherwise, Latin is probably as dead to lawyers as to anyone else.
English is now the global lingua franca; while I used to be a grammar vigilante, not long ago it occurred to me that in the linguistic "marketplace," if we native speakers want English to outcompete, e.g., Mandarin or Spanish, we need to be willing to let the language evolve so that it's easier for non-native speakers to learn and use confidently.
The same problem has to be solved in countries with more than one official language. In Ireland, the Irish-language version of a law takes precedence. This is a little awkward in theory since parliamentarians, civil servants, judges and lawyers overwhelmingly do not speak Irish to a sufficient level to draft, debate or interpret the law, and laws often exist for years before anyone gets around to translating them and thereby creating the "definitive version". But in practice, the legal system generally works.