Rules, yes, but self-adapting rules, and not rules in the form of what most people would consider as "grammar". Language operates at a much deeper level, as you can see from the fact that good translations hardly ever reproduce the most apparent grammatical structures of the original text.
On the UN producing "expert" translation, I wouldn't count on it. Most UN and EU translations better machine translation in degree only, but not in essence. They are by and large atrociously overliteral, and have little in common with natural language.
If language is algorithmic at all (and I don't think it is), it can only be so at a degree of complexity that defies reverse engineering along the lines of an electronic translator. Nobody has ever come close to writing a full grammar of any language, and I suspect the very nature of language (total open-ended versatility) is such that no such grammar can exist. This is because meaning is not encapsulated in the words of the speaker but revealed solely in the response of the listener. Words only mean what people take them to mean.
That is the first insurmountable problem for electronic translation. The second is that meaning is distributed across huge expanses of discourse. In the case of spoken language, it is distributed beyond phonetics into prosody, then beyond prosody into gesture. Written language uses a whole panoply of devices to simulate the effects of prosody and even gesture, and I don't see how an algorithmic approach could possibly allow for this.