Is NAFTA Constitutional?

By a vote of 61 to 38, the Senate joined the House in declaring that "Congress approves...the North American Free Trade Agreement." Whatever happened to the Treaty Clause? Bruce Ackerman and David Glove tell the story of the Treaty Clause's displacement in the twentieth century by a modern procedure in which the House joins the Senate in the process of consideration, but simple majorities in both Houses suffice to commit the nation. So, is NAFTA constitutional?