> 
> On Friday, three days before his resignation was made public, O'Brien told the BBC that celibacy should be reconsidered since it's not based on doctrine but rather **church tradition** and "is not of divine origin."
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> [The Huffington Post](http://www.huffingtonpost.com/mobileweb/2013/02/25/pope-changes-conclave_n_2758053.html)
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> 

Had I written that piece, I would have written "church's tradition". So the question is: Why doesn't the journalist use the genitive "'s"?