Do not go into your public library carrying a shotgun, and wander into the children's section.
And above all: don't give the lame excuse that you are doing so because you are not old enough yet for a Michigan concealed pistol license, and you are afraid that the wind might cause your coat to cover your pistol, making it concealed, and subjecting you to arrest.
Or you will discover the joy of spending time and money with lawyers. Snowflakes in Hell discusses this absurdity. The restraining order against Michigan Open Carry is here.
Is open carry lawful in Michigan? Yup, and most other states.
Am I sympathetic to someone who, for whatever reason, does not have the appropriate concealed carry permit and therefore carries openly? Well, yes, somewhat. In many states, open carry is constitutionally protected. If you have good reason to be concerned about your safety (not to make a political point), this may be the only realistic alternative.
It is bad politics, however, and carrying any sort of long gun into a public library--and into the children's section of the library--is cuckoo for Cocoa Puffs bad politics.
You know that the Republic is headed down when people become so enamored of their beautiful ideology that they don't spend enough time considering the likely political consequences of their actions.