Overlap among international institutions affects the strategic options that are available to actors. Yet no existing approach fully explains who benefits from regime complexity. While some point to materially powerful actors, others highlight weaker challengers of the status quo. Drawing on historical institutionalism, I conceptualize two dimensions of complexity. I argue that depending on the mode of interaction among the institutions in and the degree of institutional fragmentation of a governance area, opportunity structures for weaker challengers are more open or closed. Shifts on these dimensions over time thus lead to an opening or a closure of opportunity structures for challengers. I assess this argument by focusing on such shifts in two areas intellectual property regulation. The article contributes to the overall topic of the special issue and advances the literature on regime complexity by highlighting the divergent effects of different forms of institutional complexity on different classes of actors.

中文翻译：

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制度复杂性和机会结构：国际知识产权监管中参与者的影响力较弱

国际机构之间的重叠影响了行动者可用的战略选择。然而，现有的方法还没有完全解释谁从制度复杂性中受益。虽然有些人指出了物质上强大的参与者，但其他人则强调了现状的较弱挑战者。借鉴历史制度主义，我将复杂性的两个维度概念化。我认为，根据机构之间的互动模式和治理领域的机构碎片化程度，较弱的挑战者的机会结构更加开放或封闭。因此，随着时间的推移，这些维度的转变会导致挑战者的机会结构打开或关闭。我通过关注知识产权监管两个领域的这种转变来评估这一论点。