If you are on summary probation for three years, can you leave the country?

Yes as long as the probation department has been asked and said it was OK.

YOu need to have their permission in writing as you will be detained when trying to re-enter this country. Without the written permission, your re-entry will be delayed and this could prove very detrimental if you have to get back to work in a timely manner. Keep the written permission paperwork with you at all times until you are back home in your proper county.