I don't think that's possible without triggers or jass. You could use the item's HP or Level or custom value to indicate its level and make a trigger:
Whenever a hero picks up an item check if the hero's level is less than the item's chosen value, if true then drop the item from the inventory.
(Items also have a field I didn't check what is that for, it's called 'Stats - Level(Unlassified). You might want to use this instead of the latter fields.)