The Philadelphia Inquirer today reports [1]:

Accusing trade unions of standing in the way of minority hiring objectives, City Council yesterday declared the $700 million Convention Center expansion open to nonunion contractors and workers - an unprecedented gesture in a city dominated by organized labor.

Union officials commonly shut out minority and nonunion contractors from such projects through so-called "project labor agreements [2]." These cynical pacts require all contractors, whether they are unionized or not, to subject themselves and their employees to unionization in order to work on a government-funded construction project.

For more information on the harmful effects of PLAs, see this study [3] from the National Institute for Labor Relations Research [4].