Because they are constitutionally protected, it is only proper to speak of them as disabled, rather than lost, so long as the subject remains a citizen or natural person, depending on whether it is a right of citizenship or personhood. The disabilities of minority do not need to be established by a court trial or hearing. However, they can be removed sooner than they would be removed by constitution or statute, by reaching a certain age. This means it is unconstitutional to disable the right to keep and bear arms to a class of persons by statute, including those, such as felons, who have been the subject of due process on another issue, except through a proceeding in which the court is explicitly petitioned to disable them, the subject has an opportunity to argue to the contrary, the petitioner has the burden of proof that the subject if armed would be a threat to himself or others, and the court grants that petition. Merely being convicted of a crime, or declared mentally incompetent, is not sufficient if the language of the judgement does not also explicitly disable the right to keep and bear arms, or set restrictions on such right.
All citizens have such power.
Since citizens have general police powers, they also have the right to such means as they require to exercise such powers in situations in which they may be called upon to do so. That includes arms. To be constitutional, state laws restricting the bearing of arms must distinguish between public property, private commercial property which serves the public and which therefore confers certain rights to the public, and other private property with no public access rights. It is reasonable and constitutional to prohibit persons from bearing arms onto purely private property without notifying the owner or manager and obtaining his or her permission, except over public easements, such as sidewalks or the walkway from the street to the front door. On the other hand, it would be an undue burden on the right to bear arms to forbid persons from traveling between places where they have a right to be, and to bear arms while they do so, along public pathways or private easements, and using their own or a public means of transportation.