You can not "own" a /24 block. And if your membership lapses, then your blocks are returned to the general pool.
It's possible that your block is a part of a legacy allocation, they are governed differently.
It's possible that your block is a part of a legacy allocation, they are governed differently.
This timeline suggests that it's still a legacy allocation. The new governance structure does not apply unless you sign an RSA or LRSA agreement with ARIN.