Martić claimed that his actions were in response to persecution of the Serb population by the Croatian authorities.  Accordingly, he submitted defences of reciprocity or tu quoque; reprisal; and self-defence. 

Martić claimed reprisal in respect of the shelling of Zagreb.  The Appeals Chamber upheld the Trial Chamber’s finding that the two requirements for reprisal – (i) the actions in question were a valid measure of last resort and (ii) a formal warning had been given to the other side – were not met.

263. On the question of reprisals, the Trial Chamber first recalled that a belligerent reprisal is an otherwise unlawful act rendered lawful by the fact that it is made in response to a violation of international humanitarian law by another belligerent.[1] It stated that a reprisal is subject to strict conditions and is only to be used as an exceptional measure.[2] Moreover, the Trial Chamber held that, even if Croatian units had committed serious violations of international humanitarian law as alleged by Martić, two of the other conditions that justify a reprisal would not have been met. First, the shelling was not a measure of last resort, because peace negotiations were conducted during Operation Flash until 3 May 1995.[3] Second, the RSK authorities had not formally warned the Croatian authorities before shelling Zagreb.[4] As a result, the Trial Chamber held that the shelling of Zagreb was illegal because it was not shown that the conditions justifying a reprisal had been met.[5]

At paras. 265-267 the Appeals Chamber held that Martić had failed to show that the Trial Chamber erred in interpreting the evidence in relation to the two conditions.