Is で the primary way of introducing a modifying actor into a sentence?


I came across this english sentence tonight:

> "The rebel and government groups held talks mediated by the UN."

Which I loosely translated as:

> 反乱の政府はUNで取り締まる会議を開催した。

Is using で the correct way to introduce secondary actors into a sentence or
can が be used as well? Such as `反乱の政府はUNが取り締まる会議を開催した` or
`ミキさんは神で/が作ったチョコを食べた。` （Micky ate chocolate made by God).

If が is not right, is there an ambiguity in the first sentence that the talks
were being mediated **at** the UN rather than **by** the UN and how would I
communicate explicitly that its the organisation of the UN doing the thing
without using that particle?




First, I think that you should use 反乱軍代表(者), 反乱代表(者), 反政府軍代表(者), etc. instead
of just 反乱.

AのBは pattern is inappropriate for the first part. AとBは or simply inserting a
comma between A and B would be correct （反乱代表 と 政府代表）.

UN could also be 国連, the Japanese abbreviation for the UN, or the full
Japanese name 国際連合.

As で is more colloquial, you should probably use the more literary にて in this
case:

> 反乱代表者と政府代表者はUN（国際連合）の調停/仲裁/仲介にて会談を開催しました。

There is likely already a determined format for saying this in Japanese
newspapers. I will yield to more Japanese newspaper savvy commentators on this
subject.

Addressing your question about using が, it is allowable with a past indicative
verb. For で/にて you would use the passive form:

> 「AさんはBさんが作ったチョコを食べました。」'Mr. A ate chocolate made by Mr. B.'
>
> 「AさんはBさんの秘伝レシピ で/にて 作られたチョコを食べました。」'Mr. A ate chocolate made using Mr. B's
> secret recipe.'
>
> * * *
>
> 反乱代表と政府代表は国連が仲裁した会談を行いました。
>
> 反乱代表と政府代表は国連にて仲裁された会談を行いました。

