I'm not an expert, but losing France as a customer of cocoa (especially now after the panic about dwindling supplies, see http://www.ibtimes.com/chocolate-crisis-world-running-out-co...) doesn't seem like a huge deal. :) Also "oil" is generally pretty salable, there ought to be other customers.
If losing France would mean an EU embargo - which is a bit doubtful IMO - that would be more significant. But I don't think it's feasible to say that France could prevent a former colony from selling oil when we see that the so-called Islamic State in Syria and Iraq - way beyond pariah - makes significant profits in oil sales.
http://english.alarabiya.net/en/perspective/analysis/2014/08...
Economic & political pressure. If they break "agreements" they might find themselves with sanctions. Now they can't sell the cocoa or the oil. Or France would play one country against each -- "start a conflict with your neighbor in exchange for ... something"