I've read all the threads and posts (searched ARCA uptick) and I'm really confused about something that has been talked about ad naseum here. That is, whether an ECN - ISLD and ARCA are often named - allows you to sell short with no regard for an upbid or uptick. Some say that the ECNs ultimately have to follow the exchange rules, some say that the ECNs can ignore the uptick rule only when/if both sides of the order originate from them and still others say that you have blanket immunity from the uptick/upbid rule when using ARCA (some also say ISLD). Can anyone offer the correct answer and separate myth from fact? Much appreciated.