It also may be explicitly disallowed. I'm in a deadwood position on a company that's still private and the shares have a restriction that they can only be sold

It also may be explicitly disallowed. I'm in a deadwood position on a company that's still private and the shares have a restriction that they can only be sold to the company or via a deal that the company brokers. Humorously enough, while I was reading this thread, I got an email from the CFO of that company, who I haven't heard from in a couple of years now. My heart skipped a beat. :) Alas, it was not an heads up about a liquidity event...