Last month, Seattle became the second major U.S. city after San Francisco to pass a scheduling mandate on service-industry employers. These regulations, which wouldn’t look out of place in a collective bargaining agreement, force affected businesses to compensate employees for schedule changes and offer additional hours to existing employees before hiring new ones, among other provisions.

Activists are trying to expand these mandates throughout California, as well as in New York City and Washington. “With such commonsense labor standards,” argued representatives of the labor union-funded Center for Popular Democracy and Working Washington in these pages recently, “we can begin to restore balance and flexibility to our lives.”

Now the bad news: The early evidence suggests these mandates reduce workplace flexibility rather than promote it. A survey of affected San Francisco businesses, conducted by Lloyd Corder of CorCom Inc, indicates that the workplace flexibility desired by employees was reduced after the law was passed. Specifically, Corder found that more than a third of respondents now offered employees less flexibility to make their own scheduling changes.

Similarly, an analysis of the San Francisco law by the Hatamiya Group, a California consultancy, also indicated reduced flexibility. It found employees were “frustrated with not being able to change their schedules when needed,” and questioned “the need” for the mandate.

Reduced flexibility is an ironic consequence of scheduling laws because most employees affected by them seemingly select their jobs because of the flexibility. An analysis of Census Bureau data by Dr. Aaron Yelowitz of the University of Kentucky finds that only one in seven part-time employees in San Francisco is working that schedule involuntarily. (In Seattle, this figure is one in six.)

The demographics of the affected employees help explain their desire for part-time work: For instance, 28 percent of the affected employees in San Francisco are students who need a job that fits with their school schedule, compared to 6.7 percent of the entire city workforce.

Scheduling laws not only reduce flexibility but also the number of part-time jobs. Corder’s survey found that one in five affected businesses had cut back on their number of part time hires, and a similar number were now scheduling fewer employees per shift because of the mandate. Similarly, the Washington Post reported that employees were not pleased to discover “the law discourages employers from offering extra shifts on short notice, because they would have to pay the last-minute schedule change penalty,” even if the employee was voluntarily interested in working additional hours.

Fewer flexible, part-time positions and shifts may be a feature of the mandates for their labor union proponents, who believe full-time employees are more likely to view joining a union favorably. (Over 90 percent of unionized employees in the U.S. work full-time.) But this is cold comfort for the majority of part-timers who choose these positions because they offer the flexibility to pick up kids from school or attend college classes.

This evidence is unlikely to change the minds of true believers in Seattle. Witness their recent attack on a “gold-star” academic team from the University of Washington that had the temerity to conclude in a city-funded report that Seattle’s minimum wage experiment has shown some unintended consequences. The criticisms were silly, and the Seattle Times editorial page rightly condemned advocates’ “meddling with a groundbreaking, unfinished research study by our state’s flagship university.”

Still, it suggests that legislators confronted with so-called “commonsense” proposals from union-backed organizations should think carefully about whether they make any sense at all.