Think, a post apocalyptic world ravaged by nuclear wars. Most of the population has been eliminated. A small amount, but still a substantial number, a million or so people survive, residing in special domed cities to be safe from the effects of radiation. A certain number of people also reside outside, taking proper precaution to safeguard themselves against the radiation.
In this scenario, what could justify the absence of all modern weapons, be it a simple handgun to grenades to missiles to nuclear bombs (the wars kinda used all of the bombs up)? Simple medieval weapons like swords or spears, are ok.
One justification I could think of was that the people had simply adopted a pro peace attitude and destroyed the weapons towards that end but it does not completely cover the scenario as there maybe some weapons hidden, as everyone would not take that stance and, it being a post apocalyptic world, people would want to hang on to weapons to ensure their survival.
I want to weed out all weapons, no exceptions. Is it possible to achieve this ?
Edit (clarifications based on comments below) :
The enforcers, who control these people and regulated entry into the dome, have psychic powers and do not have any dependence on any weapons
For the sake of the question, modern weapon means any weapon which has a dependency on gunpowder or any kind of explosive or relies on any chemical reaction (this includes bio materials). So a trebuchet is good but a tank is a no-no. So a slingshot or a crossbow is OK but a harpoon is not allowed.