From Ardrana

When the priest casts a sanctuary spell, any opponent attempting to strike or otherwise directly attack the protected creature risks losing track of and totally ignoring the warded creature for the duration of the spell. While protected by this spell, the subject cannot take direct offensive action without breaking the spell, but may otherwise act in any way.

Note: This version of sanctuary originally appeared in the 2nd Edition Player's Handbook for Advanced Dungeons & Dragons from TSR. Its use here is for the purposes of providing context for the campaign only.