Relax. Dial your outrage back a bit.
Those aren't explosives. They aren't even "grenades".
Those are inert mortar rounds, probably left over, picked up, from the Vietnam War & all the little messes afterwards.
There are no explosives inside, and they don't have fuses to make them explode. It is obvious because the mortars are sitting on their noses where the fuses would be screwed-in to arm them.
They are as dangerous as scrap metal.
This jug-head probably wanted to bring some souviners home. Whether legal or not, they are not active explosives.