yes, yes, I know it's French, but that's what the International Chamber of Commerce Rules of Arbitration call them in English. In Louisiana, they call them amicable compounders, but I don't think that's in use anywhere much else. They decide 'by reference to considerations of general justice and fairness', mitigating a little of the strictness of the law in favour of natural equity.

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Note added at 51 mins (2010-07-10 16:09:59 GMT)
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to get the 'arbitri' in, you coud say "arbitrators acting as amiables compositeurs"

I think the Italian is a double tautology, because (a) arbitration is by definition an attempt to reach an amicable settlement, and (b) "compositori" means "attempting to reach a settlement". So just "arbitrators" will do.
Lanna's "amiable compositeurs" may be technically correct, but 99% of people will never have heard this phrase (I hadn't).