在探討貿易自由化後政府策略性運用環境政策的文獻中，多以討論出口國政府利用環境政策取代貿易政策所造成的效果及福利變化，然而世界貿易組織的形成亦造成各國平均關稅降低，但探討進口國貿易政策鬆綁後，對出口國策略性環境政策的影響，在文獻中卻少有著墨，此即本文探討之重點。
　　本文沿用Ulph(1997)所構建之模型，與其不同點在於本文考慮進口國課徵一從量關稅，並依此分別探討廠商進行Cournot 和Betrand 競爭下，政府策略性行為的變化。
　　由本文推論之結果，當廠商的市場行為是Cournot競爭時，進口國調降關稅會讓出口國的污染稅率上升，表面上環境稅率的上升，似乎意涵政府對廠商的補貼減少，且環境品質可能變得更好。但事實上應觀察的指標為邊際損害大於污染稅率的部分，此為廠商獲得的真實補貼率，由本文發現，關稅下降事實上是造成補貼率上升，換句話說生產國政府有更強烈的誘因進行生態傾銷。此外，污染稅率的提高並不足以抑制廠商增加產出造成的污染，所以關稅下降導致環境品質惡化（race to the bottom）。
　　而當廠商的市場行為是價格競爭時，關稅調降同樣會導致出口國污染稅稅率上升。然而在價格競爭底下，嚴格的環境政策對廠商是有利的，所以我們觀察另一指標，即污染稅率大於邊際損害的部分，視為對廠商課之出口稅，由本文發現，關稅下降會導致出口稅上升，表示政府藉由政策面協助廠商的態勢是更明確的。另外，如同在數量競爭的情況，關稅降低會導致環境品質惡化。
　　在兩種不同市場行為之下，進口國關稅下降，皆造成出口國福利上升，進口國福利下降；若考慮世界福利，則貿易自由化後會導致世界福利上升。從個體的角度而言，消費者與生產者均會得利，但對生產國環境將有不利影響。

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