In Building and Construction Trades Council of the Metropolitan District v. Association Builders & Contractors of Massachusetts/ Rhode Island, Inc. ("Boston Harbor"), 507 U.S. 218, 113 S. Ct. 1190, 122 L. Ed. 2d 565 (1993), the United States Supreme Court discussed PLAs in terms of business opportunities and the NLRA. In Boston Harbor, the Massachusetts Water Resources Authority was ordered to clean up the harbor and negotiated a contract with the Building and Construction Trades Council. The agreement required each successful bidder to abide by the labor agreement's terms. The respondent, representing non-union labor, sought to enjoin the agreement, arguing that it was pre-empted under the NLRA. The Supreme Court held that the NLRA did not expressly pre-empt enforcement by a state authority acting as the owner of a construction project. However, it carved out two distinct implied pre-emption principles: "Garma pre-emption" forbids state and local regulation of activities that are protected by 7 of the NLRA or constitute an unfair labor practice under 8, while "Machinists pre-emption" prohibits state and municipal regulation of areas that have been left to be controlled by the free play of economic forces. These pre-emption doctrines apply only to state labor regulation, see, e.g., Machinists,10 427 U.S. at 144. A State may act without offending them when it acts as a proprietor and its acts therefore are not tantamount to regulation or policymaking. Permitting States to participate freely in the marketplace is not only consistent with NLRA preemption principles generally but also, in this case, promotes the legislative goals that animated the passage of the NLRA's 8(e) and 8(f)11 exceptions regarding prehire agreements in the construction industry. Boston Harbor, 507 U.S. at 219. The Court went on to state that it has consistently held that the NLRA was intended to supplant state labor regulation, not all legitimate state activity that affects labor, and permitting states to participate freely in the marketplace is consistent with NLRA pre-emption principles generally. However, it also noted that the state was excluded from the definition of the term "employer" under the NLRA, see 29 U.S.C. 152(2), and the state was acting as a purchaser rather than an employer. It stated: It is evident from the fact of the statute that in enacting exemptions authorizing certain kinds of project labor agreements in the construction industry, Congress intended to accommodate conditions specific to that industry. Such conditions include, among others, the short-term nature of employment which makes posthire collective bargaining difficult, the contractor's need for predictable costs and a steady supply of skilled labor, and a long-standing custom of prehire bargaining in the industry. There is no reason to expect these defining features of the construction industry to depend upon the public or private nature of the entity purchasing contracting services. To the extent that a private purchaser may choose a contractor based upon that contractor's willingness to enter into a prehire agreement, a public entity as purchaser should be permitted to do the same. Confronted with such a purchaser, those contractors who do not normally enter such agreements are faced with a choice. They may alter their usual mode of operation to secure the business opportunity at hand, or seek business from purchasers whose perceived needs do not include a project labor agreement. In the absence of any express or implied indication by Congress that a State may not manage its own property when it pursues its purely propriety interests, and where analogous private conduct would be permitted, this Court will not infer such a restriction...Indeed, there is some force to petitioners' argument that denying an option to public owner-developers that is available to private owner-developers itself places a restriction on Congress' intended free play of economic forces identified in Machinists. Boston Harbor, 507 U.S. at 231.