Most people will obey safe storage laws, and they do cut down on accidents.
http://www.ncbi.nlm.nih.gov/m/pubmed/9315767/RESULTS: Laws that make lgun owners responsible for storing firearms in a manner that makes them inaccessible to children were in effect for at least 1 year in 12 states from 1990 through 1994. Among children younger than 15 years, unintentional shooting deaths were reduced by 23% (95% confidence interval, 6%-37%) during the years covered by these laws. This estimate was based on within-state comparisons adjusted for national trends in unintentional firearm-related mortality. Gun-related homicide and suicide showed modest declines, but these were not statistically significant.
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Not everyone will obey safe storage laws, but the majority of gun owners will. I find that most gun owners have a twisted sense of pride about obeying gun laws, even when they don't agree with them. A 25% reduction in accidental gun fatalities is a pretty major accomplishment.