The problem for Tom and Katie was simple: Scientology is not a recognized religion in Italy (where they know a sham when they see one apparently), therefore a ceremony presided over by a Scientologist would not amount to a legal marriage. And the trouble with a Catholic ceremony would've been that, though Katie is Catholic, Tom is twice-divorced, and divorced people are not allowed to re-marry in that country (and Tom, unlike Henry VIII, is not powerful enough to form his own religion just to get around the...oh, wait - maybe he is).
So the only solution was to "officialize" the marriage in America before jetting overseas for the fake show-wedding at the castle with the fireworks and the promising to give Katie a comb and a cat and Posh Spice Beckham with her stupid hat.
And don't forget the wedding picture:
I hope Tom was nice enough to lend Katie a pair of his knee-pads.
