The premise of ICAO’s USOAP, the FAA’s IASA and the EU Third Country CAA audits is that the determination of whether a country’s efforts to regulate aviation safety meet some objective set of criteria. These three programs review the effectiveness of other sovereigns and judge them. The countries being subjected to these government-to-government inspections object asserting that there is no universal matrix against which they can be assessed.
The above-linked article reports on a dialogue between Australia and New Zealand about their respective statutes and regulations. Both CAAs have received passing marks from all three of grading authorities. The comments of the Australian CASA are quite telling:
“the New Zealand rules allowed for considerable discretion in regard to the intent of the regulations and what is acceptable for compliance”
This qualitative, comparative statement suggests that there may be some basic variance within two valid regulatory approaches. CASA has a more precise set of regulations and the Kiwi CAA gives the regulated more room to interpret the rules.
That is a very significant difference; international audits have found that a CAA was deficient because its standards were unenforceable. This commentary suggests that some degree of liberal interpretation is allowable.