Defendants frequently attach supporting materials to Rule 12(b)(6) motions to dismiss for failure to state a claim. The plain text of Federal Rule of Civil Procedure 12(d) dictates that judges must either exclude this material or treat the motion as one for summary judgment. However, a substantial exception has emerged that threatens to swallow the rule. 

The exception, called incorporation by reference, permits the consideration of outside materials when they are either referenced in the pleadings, central to the claim, or sometimes both. Courts have defined these elements differently and have diverged in their understandings of the doctrine. Incorporation by reference appealingly offers an expedient route to resolve cases. But it also skirts the text and intention of the Federal Rules. This Comment explores the history of Rule 12(d), describes courts’ varying uses of the exception, and proposes a unifying method of interpretation for the future. Drawing on other procedural rules and an analogous doctrine in contract law, it argues that only unmistakably referenced written instruments may be incorporated.

被告经常在规则 12(b)(6) 动议中附上支持材料，以因未能提出索赔而驳回。联邦民事诉讼规则 12(d) 的纯文本规定，法官必须排除该材料或将动议视为即决判决的动议。但是，出现了一个可能会吞并该规则的实质性例外。 

例外情况称为通过引用并入，允许在诉状中或权利要求的核心或有时同时提及外部材料时考虑外部材料。法院对这些要素的定义不同，对学说的理解也存在分歧。通过引用并入吸引人地提供了解决案件的便捷途径。但它也绕开了联邦规则的文本和意图。本评论探讨了规则 12(d) 的历史，描述了法院对例外的不同用途，并为未来提出了一种统一的解释方法。借鉴其他程序规则和合同法中的类似原则，它认为只有明确引用的书面文书才能被纳入。