The organizational law of limited liability companies (LLCs) and partnerships has always fundamentally embraced an idea known as the “pick-your-partner principle,” under which transfers of a member’s or partner’s ownership interest are restricted by statute, and those restrictions may be tightened or loosened by agreement. In recent years the pick-your-partner principle has interacted in complex and not always practical ways with Article 9 of the Uniform Commercial Code (UCC). Since 2001, UCC §§ 9-406 and 9-408 have overridden a broad range of statutory and agreement-based anti-assignment provisions, subject to complex exceptions that have tended to protect the pick-your-partner principle in many significant respects, while also proving ana...