就像关税同盟一样，在关贸总协定规则下。

Like a customs union, free trade agreements are also legal under GATT rules.

俄罗斯到现在为止希望将石油排除在关税同盟之外。

Russia wants to keep oil out of the union for now.

布鲁塞尔已发出警告，如果乌克兰加入关税同盟，那么将会威胁到其与欧盟的关系。

Brussels has warned Ukraine that, were it to join this customs union, it would jeopardise its partnership with the EU.