The federal and Arizona constitutions prohibit the government from taking land except for a "public use" (and with compensation). Seizing land from one lawful business to give to another is hardly what the Framers' envisioned as a "public use". But this was before the age of urban renewal, where every state and local government saw itself as the central engine of economic growth. Mesa's argument to the Court of Appeals demonstrates this hubris in spades:
The City responds that the public will benefit from this redevelopment because a portion of the downtown area will be revitalized, creating an attractive “gateway” to downtown Mesa; substantial aesthetic enhancement will be achieved; property values will increase; jobs will be created; and tax and utility revenues will increase. These public benefits, argues the City, are sufficient to satisfy the “public use” requirement.The city makes no mention of property rights, presumably because the city leaders don't consider the protection of such rights to be their function. The city is more concerned with enhancing its tax revenue, which in turn provides more funds for the government to spend on favored programs.
(Mesa's property values argument is also quite amusing; are real estate agents selling houses in the area by arguing "there's a newly expanded Ace Hardware nearby"?)
The courts have held that the government may take "blighted" property--i.e., slums--from private owners and give said property to other private interests. This simply created a pretext, however, for much of the eminent domain abuse that now takes place. Most local officials define "blight" as land that's not generating as much tax revenue as possible. Other cities look at "blight" in terms of the economic prestige of certain businesses. When New York officials seized a private office building under the "blight" pretext for the benefit of the New York Times Company, city officials acted out of fear that the Times would move to New Jersey, inflicting a psychological blow to New York's political and economic communities. Viewed in this light, blight takings are more about faux self-esteem than they are meeting legitimate governmental needs.
IJ, which represented the Baileys, can use this Arizona victory to bolster their eminent domain cases in other states. This case is in fact a tribute to the virtue of fighting a cause despite the long odds. For every defeat IJ has suffered on eminent domain issues, all it takes is one victory like this one to give the cause new life within the public and judicial spheres.