From Nebraska Attorney General's Opinion no. 23-009, released Dec. 15, 2023 but just posted on Westlaw:
Municipalities lack authority to regulate the possession of firearms and certain weapons in quintessential public spaces, such as parks, trails, and sidewalks. A statute enacted in 2023, L.B. 77, deprives municipalities of regulatory authority over the possession of firearms or other weapons. And municipalities cannot use their common law proprietary authority to evade this regulatory restriction. Additionally, a blanket ban on firearms possession in such spaces would infringe constitutional rights under the Second Amendment and the Nebraska Constitution.
This year, the Legislature passed L.B. 77, which, after becoming law, significantly changes the way the possession, carriage, and sale of firearms and other weapons are regulated in Nebraska. Relevant here, L.B. 77 declared the regulation of the "ownership, possession, storage, transportation, sale, and transfer" of weaponry to be a "matter of statewide concern" and stripped municipalities of nearly all regulatory authority in that space. In the wake of L.B. 77's passage, several Nebraska municipalities [including Omaha and Lincoln] have issued executive orders that purport to restrict or ban the possession of weaponry on property the municipality owns or controls. These orders include public buildings (such as courthouses), and in some cases expand beyond buildings to include quintessential public places that are usually held open to the public at large, such as parks, trails, and sidewalks.
You have asked whether existing law "prevent[s] Nebraska municipalities from regulating the possession of firearms and other weapons in public spaces, e.g., public parks, trails, and sidewalks." It does. You have also asked whether additional legislation would be necessary to prevent municipalities from regulating weapon possession in these places. None is needed. Municipal action— regardless of the form it takes (enacted ordinance, executive order, informal policy, etc.)—that restricts or bans the possession of weaponry in quintessential public spaces, like those public places identified in your opinion request (parks, trails, sidewalks, and the like), violates at least two rules of law.