Some of the restrictions on capture provided for in this Convention were previously applied by virtue of settled practice. This was the case particularly for coastal fishing boats and for vessels engaged in scientific discovery. The Convention extended the immunity to further cases. For military hospital ships, immunity from capture is provided for in Article 22 of Geneva Convention (II) of 1949.
D.Schindler and J.Toman, The Laws of Armed Conflicts, Martinus Nijhoff Publishers, 1988, pp.819-823.