“Now, they have a huge, huge, huge battle on their hands,” said Wachter, referring to the NRA. “Because it will spread to other states.” She added: “This is a cancer. Seattle was a test bed for this initiative and it passed.”

Anette Wachter, a six-time USA Shooting rifle team champion who led the campaign against Initiative 594, said the National Rifle Association underestimated the fight put up by gun-control advocates.

Initiative 594 was designed to plug loopholes in gun laws by mandating background checks for private arm sales and gun transfers. On Election Day, voters made their voices heard loud and clear, passing the measure in a landslide – almost 60 percent to 40 percent .

Like most attempts to pass stronger gun laws, the effort to expand background checks in Washington was held up in the state Legislature for years. Lawmakers were afraid to touch the controversial issue, and gun rights advocates showed up in force at the Capitol every time it came up.

So, supporters of stricter gun laws took a new approach bypassing the lawmakers – collecting more than 250,000 signatures to put the issue to a popular vote.

Wachter, a shooting instructor, said the new law has left gun owners confused and worried that police could consider gun owners' actions to be criminal. But others such as Sandy Brown, who helped lead the 594 campaign, claim that the new law will have a big impact on violent crime, targeting private gun sales over the Internet that are currently exempt from background checks.

“In our research, we learned that there are about 40,000 guns that are available online in Washington state every year that would be sold without a criminal background check,” said Brown, president of the Center for Gun Responsibility. “So, that becomes a source for illegal guns.”

Gun-control advocates in other states, including Nevada and Maine, watched the 594 initiative closely, hoping to craft campaigns that will duplicate Washington state's results.