In the world of credit default swaps, it is "The International Swaps and Derivatives Association" - essentially the issuers of credit default swaps - that determines whether default swaps are triggered. For example the Greek debt restructuring (whereby creditors lost half their principal and the remainder is paying a low rate on a longer term) is NOT recognized a 'credit event'. The International Swaps and Derivatives Association is both judge and party. Unfortunately this is hardly an exception, considering that issuers of default swaps rarely have the capital necessary to assume pay-out of any major credit event.
On the other end, there are the fraudulent bets, taken by parties who don't own the bonds insured: who are NOT creditors and are merely placing a bet on a company or public authority declaring bankruptcy.
Why am I thinking about the Greek myth when Augias was asked to clean that stable?
J.P. Morgan losses
In April 2012, hedge fund insiders became aware that the market in credit default swaps was possibly being affected by the activities of Bruno Michel Iksil, a trader for J.P. Morgan Chase & Co., referred to as "the London whale" in reference to the huge positions he was taking. Heavy opposing bets to his positions are known to have been made by traders, including another branch of J.P. Morgan, who purchased the derivatives offered by J.P. Morgan in such high volume. Major losses, $2 billion, were reported by the firm in May, 2012 in relationship to these trades. The disclosure, which resulted in headlines in the media, did not disclose the exact nature of the trading involved, which remains in progress. The item traded, possibly related to CDX IG 9, an index based on the default risk of major U.S. corporations, has been described as a "derivative of a derivative".
As currently reported on wikipedia: https://en.wikipedia.org/wiki/Credit_default_swap