The remains of Yugoslavia's last king — Peter II Karadjordjevic, who died in the U.S. in 1970 — were flown back to Serbia in a solemn ceremony on Tuesday, despite protests by some Serb royalists in America.

The former king fled the Nazi occupation of Yugoslavia at the start of World War II and never returned because Communists took over at the end of the war. He died in exile at the age of 47 and was buried at a Serbian Orthodox Church monastery in Libertyville, Illinois — the only European monarch laid to rest on U.S. soil.

His son — Crown Prince Alexander, who lives in Belgrade — wanted the remains returned to Serbia. That reportedly upset some Serbian-American groups, who claimed the remains were being secretly exhumed and that before the king had died he asked to remain buried in the United States....