Of course they could have the right to kick someone out - but they really shouldn't have the right to say that I "quit" when I didn't.
A more apt illustration might be in a work environment. Say an employee doesn't show up for a week, doesn't call or anything. At some point, the employer has the right to declare that the employee has resigned by his actions. It isn't necessary for the employer to fire the employee. This can be important particularly when claims for unemployment benefits are disputed.
However, that doesn't really parallel JW disassociations in most cases - persons who simply stop going to the KH or out in service are not regarded as disassociated. The question revolves about persons who take positive actions (such as celebrating holidays, accepting blood, joining the military etc.). Have they "resigned" from the organization by their actions or are they being "fired"? Well, look back to the employment example. Suppose that, instead of simply not showing up, the employer caught the employee "stealing time" by not working when he was being paid to do so? Can the employer simply declare that the employee has resigned by his actions? What if the employee was caught fighting, or selling drugs in the workplace, or embezzling? Can the employer declare that the employee has resigned by his actions? Not likely, and any employer who tried to take such a position would probably be laughed out of court.
I think you have made an excellent point in this thread, and it would be really interesting to see someone who was declared "disassociated by his/her actions" take the case to court. I'm not sure they'd win (those WT lawyers have a lot of tricks up their sleeves), but it might force the WTS to once again change its policies.