International Criminal Court (as explained by the BBC)

With the warrant having been issued for Omar al-Bashir's arrest, the BBC has posted lots of information on their website about both the situation in Sudan and the International Criminal Court.  This Q&A about the International Criminal Court is both informative and interesting.   A particularly important point concerning al-Bashir's arrest which is addressed in the Q&A is that the court relies heavily on national police forces to carry out any arrests.

The ICC has no police force of its own to track down and arrest suspects.  Instead it must rely on national police services to make arrests and seek their transfer to The Hague. [For example] Thomas Lubanga was handed over to the court by authorities in the Congolese capital, Kinshasa.

My question in regards to this particular point is how do you arrest the leader of a country who is still in power and controls the military forces?  

Also, check out the questions concerning the role of the U.S. with the International Criminal Court.