One of the great debates in the in the civilian ex military jet market is what exactly is the legislation regarding use and operation of ejection seats. It would seem that there are no hard and fast rules, and once the aircraft has a certificate announcing its airworthiness the owner can make modifications to the seats to render them non functioning.
One of the biggest fears of not having functioning seats is thet in a jet aircraft you have a ton or so of heavy metal behind you anfd if you stop v suddenly in a forced landing the engine could keep going and punch through the bulkhead!
Ejection seats kept live are a must in my humble opinion.
Further reading-
Civil legislation
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