Plastic litter is introduced into the oceans from land-based sources located in many countries around the world. Marine plastic pollution may therefore be attributable to multiple states, resulting in shared state responsibility. This article discusses the issue of shared state responsibility for land-based marine plastic pollution by examining (i) primary rules of international law concerning the prevention of land-based marine plastic pollution; (ii) secondary rules of international law on this subject; and (iii) possible ways of strengthening the primary rules. It concludes that the barrier for the invocation of state responsibility may become higher in cases of shared state responsibility. Three cumulative solutions to this problem are proposed: elaborating the obligation of due diligence, strengthening compliance procedures, and interlinking regimes governing the marine environment and international watercourses.

塑料垃圾从世界上许多国家的陆地来源进入海洋。因此，海洋塑料污染可能由多个国家造成，从而导致各国共同承担责任。本文通过研究（i）有关预防陆源海洋塑料污染的国际法主要规则，讨论了国家对陆源海洋塑料污染的共同责任问题；㈡ 关于这一主题的国际法次要规则；(iii) 加强主要规则的可能方法。其结论是，在共同承担国家责任的情况下，援引国家责任的障碍可能会更高。针对这一问题提出了三个累积解决方案：细化尽职调查义务、强化合规程序、