Britain's Labor Party or Labour Party?

It looks as if an AP style rule I long disagreed with has slipped out of the book without my notice.

The old entry on Labor Party said "Not labour, even if British."

I never could figure out why we'd Americanize the spelling of a proper noun. And now future generations won't have to try.

The AP Stylebook online doesn't have the Labor Party entry. But, under spellings, it says, "British spellings, when they differ from American, are acceptable only in particular cases such as formal or composition titles: Jane's Defence Weekly, Labour Party.

A thread at Testy Copy Editors goes over the ins and outs of why it is a good or bad call. You know my opinion on the matter.

(And note Paul Wiggins' comment: "Whatever side of the fence uncomfortably straddle on this - Austrailian Labor Party please, even though labour is used here for every other use. The reasons are horribly historic and fully functional."