From 1st June 2020, foreigners residing in Korea are asked to get reentry permit before leaving Korea and to submit medical report from departing country evidencing the absence of coronavirus symptoms. The medical screening must be done within 48hours of air travel. The written diagnosis report can be either in Korean or English, it should be issues by an authorized local medical institute and include the date/signature of a medical examiner. The report must indicate if the traveler has fever, cough, chills, headache, difficulty breathing, muscle pain and pulmonary symptoms. A negative Covid-19 result will also be submitted.
The Hi Korea website, e-government services for foreigners, cited that these requirements are implemented in accordance with the article 30 of the immigration act of Republic of Korea.

Leaving the country without a permit will lead to the automatic cancellation ARC status.

These restrictions are placed for all types of VISA, except Diplomatic and overseers Korean VISA.
But these restrictions will not be applied for ARC holders left country before 1 June 2020.