As far as I know he wanted to go and "defend" his country.

The argument that he may put the other soldiers lives at risk by being there is legitimate, and obviously the fault of the media for broadcasting to the world that he might be going. His presence will endanger other soldiers, if he were there and the enemy were able to isolate him. This is a possibilty.

But at the end of the day the soldiers lives are already in serious danger as a result of the fact the previously stable dictatorship has now been stirred up into a bloody civil war.

The real reason I think is not the possible increase in danger to other soldiers, its the danger to Harry. This would not look very good for the government, certainly not in the shadow of the Diana conspiracies, and definately not in light of the fact its (a) still an illegal war and (b) not exactly going very well for the british and american forces at the moment.

Harry said that he would quit the forces if he wasn't allowed to go, but I think he has been told to stay so as not to make too much of a mockery of the whole situation.