Add these to your file of laws that don't do what their proponents claimed:

From the University of Virginia's website:

The Brady Bill, the most important piece of federal gun control legislation in recent decades, has had no statistically discernable effect on reducing gun deaths, according to a study by Philip J. Cook, a Duke University professor of public policy, economics and sociology.

From the Social Science Research Network:

The Costs of Wrongful-Discharge Laws

DAVID H. AUTOR
Massachusetts Institute of Technology (MIT) - Department of Economics; National Bureau of Economic Research (NBER)
JOHN J. DONOHUE III
Stanford Law School; National Bureau of Economic Research (NBER)
STEWART J. SCHWAB
Cornell Law School

We estimate the effects on employment and wages of wrongful-discharge protections in the United States. Over the last three decades, most U.S. state courts have adopted one or more common law wrongful-discharge doctrines that limit employers' discretion to terminate workers at-will. Using this cross-state variation with a difference-in-difference framework, we find robust evidence of a modest negative impact (-0.8 to -1.6 percentage points) of one wrongful-discharge doctrine, the implied-contract exception, on employment to population rates in state labor markets. The short-term impact is most pronounced for female, younger, and less-skilled workers, while the longer term costs appear to be borne by older and more-educated workers - those most likely to litigate under this doctrine.

[I.e., laws that require employers to have a "good reason" for firing people actually reduce employment rates.]

From Regulation magazine:

The Unintended Consequences of the Americans With Disabilities Act -- Contrary to legislative intent, ADA makes the disabled less employable.