A searcher reported a bug that Google confirmed in the Google Web Search Help forums saying that the country filter search tool doesn’t work right.

If you search within a country specific Google property, such as at google.co.nz, under search tools, you’ll see a country filter drop down to filter results only from “Country: New Zealand.” But for some folks, that filter is not working.

Here is a screen shot showing the filter set but the results showing web pages from ccTLDs that are not co.nz:

AJ from Google commented on the thread confirming that Google will look into the bug:

Forum discussion at Google Web Search Help.