This article examines the rationales for addressing sustainability and social inclusion in trade policy and the tradeoffs among imperfect institutional choices in doing so through ‘flanking policies’. It examines three types of negative spillovers or externalities implicated by trade: material, moral, and social/political. Section 1 defines terms and sets forth the argument. Section 2 typologizes the three categories of negative externalities and then highlights the challenges posed for flanking measures given the reciprocal nature of externalities. It respectively addresses environmental harms and labor and social inclusion concerns. Section 3 assesses different institutional alternatives for addressing negative externalities, dividing them between domestic measures targeted at protecting domestic concerns and international ones, such as package treaties. Section 4 shows how the concept of a flanking measure can be flipped, so that environmental sustainability and social inclusion become the core and trade measures become the flanking policies. Section 5 concludes.

This article studies the incorporation of package treaties in domestic law and administrative practice, including the functions these treaties serve once in force. This sketch of the domestic operationalization offers a window into the institutional design choices that shape how lawmakers craft the regulatory ecosystem in which flanking policies are carried out. The typology for understanding how governments situate package treaties in their domestic regulatory spaces is introduced, arguing that the ‘package’ of legally binding trade liberalization commitments and mutually agreed flanking policies is shaped by both legislative and regulatory choices that are often underestimated and overlooked. DUS trade agreements are used as a case study, finding that the US government's treatment of each of its trade agreements tends to follow a common pattern: only a small part of the agreement is transposed into domestic law; complex and robust institutions are built around the agreement to embed it deeply into the trade policy work of the executive branch; and, the entrenchment of US trade agreements has a significant enabling effect across a wide range of cross-border regulatory engagements that US agencies think of as ‘monitoring’ or ‘enforcing’, among other labels. Finally, the policy choices against the goals laid out by proponents of package treaties are assessed.

The conventional approach to trade liberalization has been to liberalize trade through international agreement and address subsequent domestic fallout and spillovers through domestic policies. In consequence, international obligations in trade liberalization are not legally connected with ‘flanking’ measures to address their negative effects. We discuss the shortcomings of this conventional approach with respect to labor adjustment and environmental protection: for political reasons, trade liberalization requires today the simultaneous regulation of labor and environmental spillovers. We suggest a novel approach to trade liberalization that includes the necessary flanking policies as part of, or linked to, the international agreement itself. This novel approach seeks to achieve the best of both worlds: reaping the benefits of international trade while making sure that negative spillovers are effectively addressed. To illustrate the intricacies of this approach, we introduce a new conceptual framework covering the negative effects of trade liberalization and flanking or mitigating policies, and a proposed novel approach in the form of trade liberalization packages and package treaties. Trade liberalization packages and package treaties are currently emerging around the world (e.g. sustainable palm oil in EFTA–Indonesia) and deserve our close attention.