Editors' Summary: This Article explores the legal and practical issues that arise where globalization and federalism intersect. A number of states and provinces in the western part of North America have joined together to reduce greenhouse gas emissions through a cap-and-trade program. The agreement passes scrutiny under the U.S. Constitution because it is essentially a voluntary measure intended to strengthen traditional forms of domestic environmental regulation. Though such strong cross-border measures have never been implemented before, they are a novel tool for dealing with regulatory issues that will increasingly arise as federalism and globalization intersect more often in the future.