Calling Method "Disable" on ComplianceRule fails, both in Properties page and in CallMethod, but the Tasks "Disable rule" works?

On attempting to disable compliance rules programmically(after Attestation Deny), the "Disable" CallMethod appears to do nothing. 

Manually clicking/using Object Browser's Method definitions or Manager's Tasks for "Disable rule" works, but calling the "Disable" method from CallMethod, or even from the Properties page Method dropdown in Manager, just returns Null. 

Is this a bug or am I doing something wrong?

Thanks in advance!