Given as established that people have a right to have guns, and carry it for self defense, how do you concretely implement it?

Meaning what are the rules, if any, that determine who can own guns, what guns, and how.

Can everyone own guns?

Can mentally ill people own guns?

Can ex criminals own guns? Maybe only some based on what they did?

Can young 15 year olds own guns?

How long does a gun license last?

Is it a matter of principle, practicality, or a mix of both? Meaning that even if there were net negative consequences to having people owning guns you would still support it in the name of freedom?

Is it a metter of culture? Meaning that these rules actually depend on the environment they are enforced in, so a more consciencious population would be less likely to use guns improperly("improperly" relative to the almost universally held moral values of not harming others without a valid reason, that is to prevent or stop unjustified harm, or restrction of freedom to self or others).