So what is your point with this?
I never stated this should not be allowed. The OP presented moving abroad as a positive thing, I made this statement to show that it is not in the interest of Greece. Every comapny expects/hopes for a return on their investment, there is no difference for countries/governments.
Does that mean that those employees should be forced to pay back that education if they move to another company
That is not uncommon in Europe when such training is extensive and expensive. It is often provided with a clause that if the employee is leaving the company within a x number of years, an equivalent share shall be reimbursed. Often this is happily paid by the new company the person will work for.