"Certification" seems a benign enough word. But it hides an extraordinary power that the United States is expected to assert if the Trans-Pacific Partnership (TPP) is concluded.
The US basically claims the right to decide what a country's obligations are under a trade and investment agreement. It then refuses to bring the agreement into force in relation to the other country until that government has changed its laws, regulations and administrative processes to fit the US expectation of what is needed to comply. This certification process can run on for years.
Communications from the US Congress and the US Trade Representative (USTR) suggest their prime targets for New Zealand would be our copyright and patent laws, the foreign investment vetting regime, the procedures by which Pharmac operates, and Fonterra's "anti-competitive monopoly".
How does certification work? US officials transmit the list of the changes to the other country's domestic laws and regulations that they require before the US allow the pact to go into force. The officials maintain pressure on the government of the other country until they are satisfied.
The certification requirement has existed since the 1980s, but US politicians and corporates were unhappy over deals with Chile and Australia, so there has been more focus in recent years on ensuring their demands are met before the agreement comes into force.