Depends on where it's held. Some fairs are actually held on private property. Then, even if it is sponsored by a government entity, the property owner can ban weapons.
However, if it were public property and public entity, pre-emption holds, per my understanding.
Not in a position right now to check the actual statutes. Would also have to know who sponsors the fair (for example, if it's a non-governmental board) and whether they just lease the property.