Under New Jersey’s new bump-stock ban, which was approved in January, residents were supposed to destroy or turn in their bump stocks by mid-April. So far, New Jersey State Police say, they have not received a single one, reports Stateline.org. Months after a man used a bump stock to quickly mow down 58 people in Las Vegas, seven states now prohibit the sale and possession of the devices, which enable semiautomatic rifles to fire at the rate of fully automatic fire. In Massachusetts, where residents had until February to surrender their bump stocks, state police received just three devices. Bump-stock bans in Florida, Maryland, Vermont and Washington have been approved but have not yet gone into effect. Bans of bump stocks in Hawaii and Connecticut are currently awaiting governors’ signatures, and lawmakers in Delaware and Rhode Island are expected to approve bans soon.

Even though proposed bump-stock bans have stalled in more than a dozen states, gun control advocates who want to rid the country of the accessory are celebrating their existing statehouse victories. They agree with gun owners and police, however, that enforcing the bans will be a challenge. It’s hard to know for sure, but Americans could own as many as 520,000 bump stocks, according to ATF estimates. The government estimates that Americans have spent $96.2 million on bump stocks between 2011 and 2017. These devices can cost from $180 to $425 each. Many of them are untraceable, in part because they don’t have serial numbers.