ATHENS, Aug. 9 -- When Israel's Foreign Ministry issued a travel advisory Saturday urging its nationals in Greece to avoid popular tourist destinations and conceal Israeli and Jewish symbols, it was not describing a far-flung conflict zone. It was describing Santorini. It was describing Athens and the island beaches that have hosted Israeli tourists for generations. This weekend, pro-Palestinian protesters were explicitly organizing at those same sites against what they described as the genocide in Palestine, a word Israel's own government, in advising its citizens how to navigate the atmosphere, chose not to contest.

The advisory, first reported by Haaretz, is a small document with significant implications. A government that formally in...