Trade has three elements – supply, demand and the mechanism of trade. In order to address the current massive problems with the trade in endangered species, all 3 elements need to be tackled.
The justification for allowing the trade at all is currently embedded in the notion of ‘sustainable use’ – the exploitation of nature for human needs and wants in a way, and at a rate, that does not lead to the long-term decline of species (and biodiversity). It is invariably linked to ‘sustainable development’, by, for example, using wealthy countries’ development aid budgets as a way of alleviating poverty in poor range countries.
What is never discussed is that this ‘sustainable use’ is not compatible with the capitalist mode of production, which relies on endless, exponential economic growth. The commodification of nature and its exploitation for profit is a necessity under capitalism and especially under the current form of financialised, free-market capitalism. The result is exactly as one would expect – ‘sustainable use’ is never actually sustainable, all exploitation of nature is done in ways and at a rate that does lead to a long-term decline in species and biodiversity (a handful of endlessly recited counterexamples such as crocodiles notwithstanding).