Why the Max grounding challenged principle of mutual recognition

When the Boeing 737 Max was barred from the airspace of several countries by national authorities, a question arose as to whether this amounted to breaching a fundamental principle of ICAO – that of mutual recognition of airworthiness certification.

National authorities have the right to act against aircraft on their own register. But in March 2019 a number of civil aviation regulators prohibited all 737 Max services in their airspace, regardless of their operator, even as the US FAA resisted suspending its type certificate and grounding the aircraft.

This appeared to contradict an ICAO tenet enshrined in Article 33 of the Chicago Convention, that certificates of airworthiness issued or rendered valid by the state of registry shall be recognised as valid by other states.