"Did you have to pass through Customs or some other international checkpoint when you landed in Kazakhstan?"
Hadfield's answer? Yes! As the Canadian explains it, "NASA kept our passports and visas, and brought them to us at landing, so we had them at the Karaganda airport to leave Kazakhstan." The whole thing was, he says, "a funny but necessary detail of returning to Earth."
Hadfield and his colleagues weren't the first to take their triumphant return with a little dose of bureaucracy. The Apollo 11 astronauts Neil Armstrong, Buzz Aldrin, and Michael Collins had to do something similar after their return from the moon in July 1969. On the way home, after their splashdown in the Pacific, they passed through the Honolulu Airport. Where they filed a standard customs form.
The flight number they listed? APOLLO 11.
The goods they declared? MOON ROCK AND MOON DUST SAMPLES.
And the route they laid out? Florida's Cape Kennedy (now Cape Canaveral) to Honolulu, Hawaii. With a brief stopover at MOON.