I'm surprised it took them this long to do something of the sort. I can't imagine anyone's naive enough to think that China was actually going to let them stay autonomous indefinitely.
If I remember correctly it was part of the formal agreement with Britain for the hand-over of HK back to China. But yeah, quite a lot of people, myself included, were surprised at how China had seemed to be upholding that end of the deal. I guess that's all over then. You know what Britain is going to do about this violation of the agreement? Fuck all most likely.