Brands each donated $1 million to Save Local Restaurants, a coalition opposing the law.
Other top fast-food companies, business groups, franchise owners, and many small restaurants also have criticized the legislation and spent millions of dollars opposing it.
The measure, known as the FAST Act, was signed last year by California Gov. Gavin Newsom and was set to go into effect on January 1.
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Labor law in the United States is structured around unions that organize and bargain at an individual store or plant.
This makes it nearly impossible to organize workers at fast-food and retail chains with thousands of stores.
If restaurant worker compensation increased by 60%, limited-service restaurant prices would jump by up to 22%, the study also found. »