If you bought the time share for personal use, then just as in the case of a sale of a principal residence, no loss is allowed. If you bought the time share for investment purposes, you may be able to take the loss as a long-term capital loss.
A revenue ruling is the Commissioner’s “official interpretation of the interpretation of the law” and generally is binding on revenue agents and other IRS officials. Taxpayers generally may rely on published revenue rulings in determining the tax treatment of their own transactions that arise out of similar facts and circumstances.