Spouse unaccompanied in international assisgment

First, what is the personal issues that you have to take your wife? There is no legal meaning of personal issues under the labour law. 

In my opinion, there is no labour law which will let you take your wife with you. It is upto the company to decide regarding onsite assignments and it is ultimately the dsicritionary power of the management whether to allow spouse on such tour or not.

However, you can always try talking to the HR and convince him in your personal capacity.