As I recall, when the Norwegains protested to the British that Britain had violated Norwegian neutrality by entering Norwegian waters and boarding the Altmark, the British retorted that the Altmark had violated Norwegian neutrality by anchoring in Norwegian waters while retaining a cargo hold full of prisoners of war. The British also apparently implied that the Norwegians had been either openly complicit in this action or, at the very least, negligent in not discovering the German ruse. My understanding of international law is that belligerent ships entering neutral waters are required to release any prisoners of war they are carrying – a good example being, ironically enough, the British prisonners who were released in neutral Uruguay by Captain Langsdorff when the Graf Spee (the ship supplied by the Altmark) anchored in Montevideo harbour. At any rate, the British position vis a vis Norway was basically, “You drop your protest and we’ll drop ours.” Which they did.