Because the stock loss produced a tax benefit to you, the recovery is taxable. The question is whether you report the recovery as a capital gain (since you took a capital loss) or as ordinary income. Under the “origin of the claim doctrine,” it appears that the recovery can be treated as capital gain even though the lawsuit recovery isn’t a sale or exchange. But the IRS has not ruled definitively on this exact situation.
Source: https://taxprof.typepad.com/taxprof_blog/files/2005-16770-1.pdf
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.