I think you can enchant them, yup, but there are limits. To cite a few comments on the item from Wowhead:
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what happens if you enchant mongoose on these kind of weapons, and then send it to your lvl 1 alt?
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An excellent question, but heirloom items will not be enchantable with any enchants that have an item level requirement on them. Really too bad. I can see a level 10 rogue with this and something else both with mongoose on them. I suppose they made leveling easy enough though.
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Ill still be getting a nice lil 2hander with crusader for my war, and re-enchant it with something else (I think maybe +7 dmg or something) post 60.
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Crusader is still rather...ok...past 60 you know. Don't quote me on the proc rate VS stat gain percentage after 60 though.
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It has an item level of 1, so you can't put any enchant with a level requirement on it. So Crusader is gonna be the best.