Full Idea
Whenever there is some substantial chance of success, reprisals are the legitimate resort of a victim state; for no state can be required passively to endure attacks upon its citizens.
Gist of Idea
States need not endure attacks passively, and successful reprisals are legitimate
Source
Michael Walzer (Just and Unjust Wars [1977], 13)
Book Reference
Walzer,Michael: 'Just and Unjust Wars' [Penguin 1984], p.221
A Reaction
My concern is whether the reprisals have any direct connection to the attacks. They killed some of ours, so we will kill some of theirs is immoral. E.g. bombing Tripoli as reprisal for crashing the Lockerbie plane.