Note holders can go to court IF the issuer won't allow conversions. Or if Rule 144 is unavailable to the note holders because the issuer is an SEC filer that's currently delinquent.
But they can't blame the issuer if their broker or clearing firm won't clear their stock for deposit. That's been an increasing problem over the past few years. Recently it's become even worse. For example, now Alpine won't deal in stocks trading below a penny. And they charge a MONTHLY account fee of $5000.
The problem for the issuer is that if a lender is unable to sell his stock, he's unlikely to lend more in the future. But the general problem is way more complicated than that.