It's hardly illegal to expect someone to stick to the contract he signed - this request is for a change of agency working with the same airline, in which case the airline and the current agency will say loud and clear "your problem, you signed it". Restriction of your right to work doesn't include changing agency and working for the same airline! In any case, his contract may be outside the EU, or he may have signed a contract subject to law from outside of the EU. There's no "going to court" involved in this - it is between the agency, airline and contract pilot. By the way, the 12 month period is 6 months too long, sign a contract with the right agency first next time.