Project labor agreements (PLAs) are used in certain states to promote pay and benefit equity for construction workers.  Specifically, PLAs ensure that construction workers who choose not to join a union have access to the same pay and benefits as their union-affiliated colleagues.  PLAs ensure that the presence or absence of a labor union is not a factor in the contract bidding process, therefore encouraging more contractors to bid on construction projects.  Proponents of PLAs contend that they expand employment opportunities.  Opponents claim that the PLA cannot exist in at-will employment states. Which side is more correct?  How can at-will employment laws exist where PLAs are allowed?