First Principles Thinking: the stricter rule governs
B is correct. Standard I(A) requires members to comply with the stricter of applicable law, regulation, or the Code and Standards. An outdated firm manual cannot override a current legal prohibition, so the member must stop participating.
A is tempting because firms often centralize policy updates, but the member's duty does not wait for administrative cleanup once she knows the law is stricter.
C fails because disclosure does not authorize conduct that applicable law prohibits.