in a slap to

Apple loses right to iPhone name in...

Hong Kong (CNN) -- When it comes to buying an iPhone in Brazil, consumers have one extra option that the rest of us do not.

There's the "iPhone" made by the California tech giant Apple. Then there's the "iphone" made by the Brazilian firm Gradiente Eletronica and, perhaps in a slap to Apple, runs on rival Android's operating system.

And it's going to stay that way pending any future appeal or settlement.
On Thursday, Brazil's Institute of Industry Property (INPI), the country's main patent regulator, ruled that Apple holds no exclusive right to use the iPhone moniker to market its mobile phones. If Apple continues to use the iPhone name, Gradiente can sue.

http://edition.cnn.com/2013/02/14/business/apple-loses-iphone-name-brazil/index.html?hpt=hp_t3

in a slap to~は小粋な表現です。「〜にとっては平手で（顔を）はたかれるように、平手打ちを受けるように」ということなんでしょうが、「ダブルパンチ」もしくは「泣きっ面にハチ」のニュアンスが伝わってきます。（UG）