element of their networks that was "necessary" and without which competitors would be "impair[ed]" in their ability to provide service (47 U.S.C. § 251(d)(2)). The majority declined to decide whether this provision incorporated the standard embodied in the essential facilities doctrine, but Justice Breyer found the two principles to be "analogous." Tellingly, both the majority and Justice Breyer declined to compel access to any input that was available from other sources (525 U.S. at 388-92, 428). Courts implementing other statutory access mandates have been similarly reluctant to compel access to inputs that are available from other sources. 31 Acceptance of this structural precon- dition is also reflected in the nonhorizontal merger guidelines issued by the Justice Department, which now require that the primary market must surpass a certain threshold level of concentration before antitrust authorities will seriously consider challenging a vertical merger. These decisions also incorporated another of the structural preconditions sug- gested by the economic theory by requiring proof of substantial foreclosure in the secondary market before subjecting a restraint to antitrust scrutiny. The Supreme Court was even more explicit in Spectrum Sports, Inc. V. McQuillan, holding that even concededly bad conduct cannot support a monopolization claim in the absence of evidence of actual monopolization or a dangerous threat of monopolization, of the secondary market.34 Lower courts have similarly made a threat to a vertically Wholesale Stationers, Inc. V. Pac. Stationery & Printing Co., 472 U.S. 284, 296-97 (1985) (applying equivalent requirement to group boycotts). 29 See, e.g., MCI, 708 F.2d at 1132; Hecht, 570 F.2d at 992; cases collected in Areeda and Hovenkamp (2008c, pp. 242-45). 30 Consul, Ltd. V. Transco Energy Co., 805 F.2d 490, 494-95 (4th Cir. 1986); City of Malden V. Union Elec. Co., 887 F.2d 157, 160 n. 4 (8th Cir. 1989); Ill. Bell Tel. Co. V. Haines & Co., 905 F.2d 1081, 1087 (7th Cir. 1990), vacated, 499 U.S.