I know we're talking about magical elves world here, but... it really isn't possible. It's not as much that halberds are not balanced. It's like 95% of entire point of the halberd that it's not balanced.
So with a lot of pain and groaning, and being threatened that my magic would be taken away from me - I might not kill the person who allows halberd to be effectively thrown, ever. But to throw it with one hand is...
It's not really a reasonable argument to go 'Hey, look, you can't be tossing halbards easily' when said halbard is something that has magic mojo that makes it so.