Modes; The BOD aren't allowed to trade when they have inside information, and with SIAF there must be inside information almost at any given time (progress or lack thereof of the TRW-loan, F-1 filing, CA-deals etc).
I haven't been around long enough to judge whether there has been periods where they could have traded in the past though, but I have difficulties to see that they could have been allowed to ever since they colisted on Merkur.