As we know Ken seeks legal advice regularly. He wouldn't withhold Ukyo's shares unless that was something he could justify to a judge based on Ukyo withholding our BTC. Its a fair move at the end of the day and compensates for the loss of capital suffered by ACtM.

EDIT

https://bitcointalk.org/index.php?topic=297543.msg3782916#msg3782916

We have ~106 BTC in the Bitfunder/WeExchange system which we can not obtain.  We have sent Bitfunder's/WeExchange's Ukyo a Legal Demand For Payment within 72 hours.  We expect this problem to result in the loss of the 106 BTC.  We are meeting with our Lawyers to determine what our next steps will be.