Here's another source, according to which shorting against your restricted PIPE stock is permissible. http://trace.tennessee.edu/cgi/viewcontent.cgi?article=1198&context=transactions&sei-redir=1&referer=http%3A%2F%2Fwww.google.com%2Furl%3Fsa%3Dt%26rct%3Dj%26q%3Dshorting%2520against%2520pipe%2520stock%26source%3Dweb%26cd%3D3%26ved%3D0CDsQFjAC%26url%3Dhttp%253A%252F%252Ftrace.tennessee.edu%252Fcgi%252Fviewcontent.cgi%253Farticle%253D1198%2526context%253Dtransactions%26ei%3Dc2miUartL9XD4AOFjYDACw%26usg%3DAFQjCNHumZXCd_1bg_uBnvCXHPvxyYLuXw%26sig2%3D2wekpafq8vKqKR1Cr8ktcQ%26bvm%3Dbv.47008514%2Cd.dmg#search=%22shorting%20against%20pipe%20stock%22 It's from 2011, and so fairly recent. See page 24... And going ahead, there's an excellent explanation of the SEC's attitude toward shorting PIPEs, which the authors believe to be mistaken.