Korean War Service Medal (aka – Republic of Korea War Service Medal)
On 15th September 1951, President Syngman Rhee authorised the commander-chief of the United Nations to confer the award of the Korean War Service Medal and Ribbon “to the brave and valiant members of the United Nations Command who have been, and are now, combating the communist aggressor in Korea.”
In 1999, the South Korean government proposed the medal be reactivated and retroactively awarded to all Korean and U.N. veterans who had served in the Korean War. Governments of participating countries then started to make this possible. The U.S. authorised the wearing of this medal soon after, with other nations doing the same.
On 23rd April 2001, The Korean War Medal was authorised for distribution and wear by service members of the British Commonwealth. I believe that distribution to qualifying veterans from Canada, Australia and New Zealand was approved by the Queen. However the U.K. government decided not to amend its attitude. The medal can of course be worn on the right breast. (Caution: The above is based on my interpretation of this subject, collected from various sources).