The policy must be displayed either at each entrance to the store, at each cash register and sales counter, on tags attached to each item,
or on the company's order forms, if any. A return policy printed only on a receipt, for example, is not sufficient.
If a store violates this law (California Civil Code section 1723), the purchaser can return an item for a full refund within 30 days of purchase.
there you go , folks, there it is in writing from the Ca. Attorney General
So basically, I do believe you must display in your listing , in at least large font, that there are no refunds,
always correct,never wrong, but humble in my greatness