The recent incident on MV Mavi Marmara is reminiscent of a similar attempt by supporters of the Tamil LTTE in May 2009 [to get "humanitarian aid" to a terrorist group] in Sri Lankan waters. A pro-LTTE organisation chartered a merchant vessel MV Captain Ali to make a daring attempt to land material and supplies directly to areas held by the LTTE prior to the final battle.
(See this article on the incident)
The ship was detained by the Sri Lanka Navy and turned back because it did not have the proper documentation. As a compromise the ship unloaded the cargo in India and was sent across to Sri Lanka by the Indian Red Cross.
A key factor in the Sri Lankan situation was that MV Captain Ali did not have the proper paperwork relating to the ETA details. Any ship leaving a port must indicate the destination under international maritime regulations. A ship cannot leave a port with an undisclosed destination.
In the case of the international flotilla bound to Gaza, the biggest breach of international law took place in Turkish Cyprus when the flotilla was permitted to leave without a designated destination port. The fact that Turkish Cyprus is permitted to exist as an unrecognised defacto state is one of the key problems in this case. They are not guided by international obligations and provide sanctuary and opportunity for illegal transport activity.