There is a law deficit in merger cases. The Supreme Court has not decided a substantive merger law case in over four decades. There literally is no useable case law on vertical mergers — and AT&T did not create any. The situation is not that much better for horizontal merger law. This legal vacuum has been filled by the agencies’ Horizontal Merger Guidelines, which most district courts follow uncritically. The article identifies important issues of merger law that are not appropriate for resolution by agency policy statements, but deserve serious judicial consideration, preferably by the Supreme Court. The article concludes with a few tentative solutions to this problem.