How does Romer get a multiplier from this action?

Obama abandoning free labor:

Barely 15 percent of all construction-industry workers in the United States are union members, while the remaining 85 percent are nonunion, according to the U.S. Department of Labor's Bureau of Labor Statistics. So why has President Obama signed Executive Order 13502 directing federal agencies taking bids for government construction projects to accept only those from contractors who agree in advance to a project labor agreement that requires a union work force? Obama's new order applies to all federal construction projects with price tags of $25 million or more, and it means all such contracts will only be awarded to companies with unionized work forces

Like Jerry Brown, Obama is becoming a bankrupt politician.