With eleventh hour guidance from the state, Maine gun retailers on Friday began requiring a three-day wait period for gun purchases under one of the new safety laws adopted following the state’s deadliest mass shooting.

Maine joins a dozen other states with similar laws, requiring that buyers wait 72 hours to complete a purchase and retrieve a weapon. The law is among several gun-related bills adopted after an Army reservist killed 18 people and injured 13 others on Oct. 25, 2023, in Lewiston.

The new law wouldn’t have prevented the tragedy — the gunman bought his guns legally months earlier — but Friday’s milestone was celebrated by gun safety advocates who believe it will prevent gun deaths by providing a cooling-off period for people intent on buying a gun to do harm to others or themselves.

Gun store owners complained about the guidance, released just Tuesday, and the loss of sales to out-of-state visitors during Maine’s busy summer tourism season. They also said the waiting period will take a toll on gun shows.