Legality, ecigs vs shisha

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In many cities were ecigs have been banned, shisha's and hookahs are perfectly legal. Here in Hong Kong, shisha bars have sprouted up everywhere.

I don't understand how they can outlaw ecigs because:

Sale and possession of E-cigarettes containing nicotine and marketed as nicotine replacement therapy are outlawed

Yet hookah's burn tobacco (not as clean) and also contain nicotine.

Can someone explain this to me?