This article aims to explain the under-researched phenomenon of why the European Commission (the Commission), as ‘guardian of the Treaties’, tolerates member states’ noncompliance with the EU law. While major accounts of selective enforcement depict the Commission as a self-serving political entrepreneur, this paper assumes that it is a trustee guardian of EU treaties that aims to safeguard the stability and integrity of the EU legal order. For this purpose, the Commission is theorized to strategically utilize toleration of noncompliance to evade jurisdiction overlap and norm collision. Relying on the detailed tracing of the Commission's enforcement leniency towards Slovakia regarding pharmaceutical parallel trade, this illustrative case study indicates that toleration of noncompliance is a necessary evil for the Commission and other stakeholders to navigate through a legal and political impasse. And it simultaneously preserves the delicate integrity of the existing legal order of EU free movement law.

中文翻译：

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多层次系统中的法律限制：解释欧盟委员会对药品平行贸易违规行为的容忍度*

本文旨在解释为什么欧盟委员会（委员会）作为“条约的守护者”，容忍成员国不遵守欧盟法律的现象。虽然选择性执法的主要描述将欧盟委员会描述为一个自私自利的政治企业家，但本文假设它是欧盟条约的受托监护人，旨在维护欧盟法律秩序的稳定性和完整性。为此，委员会在理论上可以战略性地利用对违规行为的容忍来规避管辖权重叠和规范冲突。依靠委员会在药品平行贸易方面对斯洛伐克的执法宽大的详细追踪，这个说明性案例研究表明，容忍违规行为是委员会和其他利益相关者度过法律和政治僵局的必要之恶。它同时保留了欧盟自由流动法现有法律秩序的微妙完整性。