This is not the first time murky reinsurance transactions have been in the purview of regulators.

Both offshore insurers had financial agreements with A.I.G. that significantly minimized the risk transfer involved in certain reinsurance transactions.

Zurich Financial Services settled a bid-rigging and improper "finite reinsurance" transactions probe.

That's Accounting 101 in any reinsurance transaction.

The capital infusion became necessary to bring the company's financial position up to regulatory standards, in light of the department's assessment of the reinsurance transactions, the regulators said.

"The defendants structured two phony reinsurance transactions that had no real economic substance."

Such an argument may make it harder for Mr. Greenberg's lawyers to make the case that finite reinsurance transactions are notoriously complex.

In 2005, New York Attorney General Eliot Spitzer began an investigation into the two reinsurance transactions.

Many financial reinsurance transactions, particularly for life insurers, have little impact on GAAP accounts and shareholder-reported profits.

Regulators at Ireland's fledgling financial watchdog are facing the test of a lifetime as the trail of a suspect reinsurance transaction brings investigators to Dublin.