winkle - I think you may have your work cut out in your efforts to determine what is and is not a legal contract.
Agreeing with someone who comes to you unqualified for the position on offer that you will teach, train and qualify them for that position and in addition the employer will agree to employ them for a minimum period of return of service but, should the employee choose to leave their employment before they have completed that return of service period, then they will compensate their employer financially for the employer's loss, doesn't sound either illegal or unfair to me. Can you quote me a bond that states that the bond is conditional on the employer/employee each honouring the original contract of employment, (not 'Bond'), and in the event of a
perceived lapse the bond is void? Bonds are usually separate documents to the Contract of Employment.
(The term
'Bond' should not to be confused with actually paying hard cash up front for your own training in order to get a job, that is not a bond as is widely known in the aviation industry for the last thirty to forty years).
Please excuse punctuation, not my strong point.