San Remo Manual on International Law Applicable to Armed Conflicts at Sea,
12 June 1994
www.icrc.org/ihl.nsf/385ec082b509e76c41256739003e636d/7694fe2016f347e1c125641f002d49ce

SECTION V : NEUTRAL MERCHANT VESSELS AND CIVIL AIRCRAFT

Neutral merchant vessels

67. Merchant vessels flying the flag of neutral States may not be attacked
unless they:

(a) are believed on reasonable grounds to be carrying contraband or
breaching a blockade, and after prior warning they intentionally and clearly
refuse to stop, or intentionally and clearly resist visit, search or
capture;
(b) engage in belligerent acts on behalf of the enemy;
(c) act as auxiliaries to the enemy s armed forces;
(d) are incorporated into or assist the enemy s intelligence system;
(e) sail under convoy of enemy warships or military aircraft; or
(f) otherwise make an effective contribution to the enemy s military action,
e.g., by carrying military materials, and it is not feasible for the
attacking forces to first place passengers and crew in a place of safety.
Unless circumstances do not permit, they are to be given a warning, so that
they can re-route, off-load, or take other precautions.