Washington state is on track to become one of the strictest states in the U.S. on gun laws.

Initiative 1639, a sweeping measure to beef up gun-regulations, passed Tuesday with 60 percent of the vote, Seattle's Q13 Fox reported.

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Campaign Manager Stephen Paolini, 22, said the measure’s passing sends “a message to our elected officials: Enough is enough.”

“My generation has been defined by gun violence. We have been defined by continued and repeated inaction by our elected officials,” Paolini told a crowd of supporters after the measure passed.

Alan Gottlieb of the Bellevue, Wash.-based Citizens Committee for the Right to Keep and Bear Arms, said opponents will sue to block I-1639.

“A handful of billionaires put in millions of dollars to buy votes and we were outspent,” he said. “But while they were able to buy votes, our hope is they won’t be able to buy judges.”

“A handful of billionaires put in millions of dollars to buy votes and we were outspent. But while they were able to buy votes, our hope is they won’t be able to buy judges.” — Alan Gottlieb, Citizens Committee for the Right to Keep and Bear Arms

Other critics say I-1639 violates their Second Amendment rights and will be ineffectual in preventing mass shootings.

Barring legal challenges, the new restrictions will go effect at the beginning of next year.

The 30-page measure raises the legal age to purchase semi-automatic assault rifles and requires enhanced background checks. Purchasers must take a safety training course and must wait 10 business days from the date a licensed dealer requested the background check. The measure also mandates storage requirements and increases legal penalties on gun owners who fail to comply with the new laws.

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The initiative drew more than $5.5 million from supporters – most whom were wealthy donors, such as Microsoft co-founder Paul Allen, who died last month, the Seattle Times reported. Opposition to the measure, led by the National Rifle Association and other pro-Second Amendment groups, raised a meager $622,000.

The Associated Press contributed to this report.