巴西客户的付款方式

近来在跟一个巴西的客户 谈到付款方式，他的要求是：our desired is that the payment is made 100% after nationalization of the material. we studied against proposals. 下面好像还解释了一下：the reason for the condition of payment is sending stuff outside the norm indicated if the submitted material has divergence from the norm is possible that it is disposed of by our government agents。 这个付款方式是什么呀？怎么操作的？ 而且巴西海关刚出的新政策是凭提单副本就可以提货，这个应该怎么顺利回余款呢？