- 37 - CDL-AD(2006)009 Council of Europe member States: they must therefore refuse to allow transit of prisoners in circumstances where there is such a risk. As regards overflight i) If a Council of Europe member State has serious reasons to believe that an airplane crossing its airspace carries prisoners with the intention of transferring them to countries where they would face ill-treatment in violation of Article 3 of the European Convention on Human Rights, it must take all the necessary measures in order to prevent this from taking place. j) If the state airplane in question has presented itself as a civil plane, that is to say it has not duly sought prior authorisation pursuant to Article 3 c) of the Chicago Convention, the territorial State must require landing and must search it. In addition, it must protest through appropriate diplomatic channels. k) If the plane has presented itself as a state plane and has obtained overflight permission without however disclosing its mission, the territorial State cannot search it unless the captain consents. However, the territorial State can refuse further overflight clearances in favour of the flag State or impose, as a condition therefor, the duty to submit to searches; if the overflight permission derives from a bilateral treaty or a Status of Forces Agreement or a military base agreement, the terms of such a treaty should be questioned if and to the extent that they do not allow for any control in order to ensure respect for human rights. l) In granting foreign state aircraft authorisation for overflight, Council of Europe member States must secure respect for their human rights obligations. This means that they may have to consider whether it is necessary to insert new clauses, including the right to search, as a condition for diplomatic clearances in favour of State planes carrying prisoners. If there are reasonable grounds to believe that, in certain categories of cases, the human rights of certain passengers risk being violated, States must indeed make overflight permission conditional upon respect of express human rights clauses. Compliance with the procedures for obtaining diplomatic clearance must be strictly monitored; requests for overflight authorisation should provide sufficient information as to allow effective monitoring (for example, the identity and status (voluntary or involuntary passenger) of all persons on board and the destination of the flight as well as the final destination of each passenger). Whenever necessary, the right to search civil planes must be exercised. m) With a view to discouraging repetition of abuse, any violations of civil aviation principles in relation to irregular transport of prisoners should be denounced, and brought to the attention of the competent authorities and eventually of the public. Council of Europe member States could bring possible breaches of the Chicago Convention before the Council of the International Civil Aviation Organisation pursuant to Article 54 of the Chicago Convention. n) As regards the treaty obligations of Council of Europe member States, the Commission considers that there is no international obligation for them to allow irregular transfers of prisoners or to grant unconditional overflight rights, for the purposes of combating terrorism. The Commission recalls that if the breach of a treaty obligation is determined