The particular mode of applying pressure without going to war known as "pacific blockade" dates, as is well known, only from 1827.

It has indeed been enforced, by England as well as by France, upon several occasions, against the vessels of third Powers; but this practice has always been protested against, especially by French jurists, as an unwarrantable interference with the rights of such Powers, and was acknowledged by Lord Palmerston to be illegal.

The British Government distinctly warned the French in 1884 that their blockade of Formosa could be recognised as affecting British vessels only if it constituted an act of war against China; and when the Great Powers in 1886 proclaimed a pacific blockade of the coasts of Greece they carefully limited its operation to ships under the Greek flag.
The Subject has been exhaustively considered by the Institut de Droit International, which, at its meeting at Heidelberg in 1887, arrived at certain conclusions which may be taken to express the view of learned Europe.

They are as follows:-- "L'etablissement d'un blocus en dehors de l'etat de guerre ne doit etre considere comme permis par le droit des gens que sous les conditions suivantes:-- "1.

Les navires de pavillon etranger peuvent entrer librement malgre le blocus.
"2.