98. Merchant vessels believed on reasonable grounds to be breaching a blockade may be captured. Merchant vessels which, after prior warning, clearly resist capture may be attacked.

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.