A company uses AWS Organizations and has an SCP at the root that prevents sharing...

Service control policies (SCPs) define the maximum available permissions for accounts and are evaluated as guardrails. AWS Certified Security – Specialty documentation states SCPs are typically used to apply organization-wide restrictions, and exceptions are commonly handled by using conditions (for example, excluding specific accounts) or by structuring OUs differently. Because all accounts are in the same OU and the company must continue blocking external sharing for everyone except one account, modifying the existing SCP to exclude the marketing account is the most direct solution. An SCP attached at the root affects all accounts unless conditions narrow its scope. Adding a condition that excludes the marketing account allows that account to retain the ability to share resources externally while the SCP continues to block sharing for other accounts. Option A is not feasible because account-level SCPs cannot override a deny applied by a parent SCP; explicit denies always win. Option C misunderstands SCP behavior because SCPs do not grant permissions; they only limit. Option D is an IAM control that cannot override an organization-level deny. Therefore, the only secure, scalable option is to modify the existing SCP with an exception condition for the marketing account.

Referenced AWS Specialty Documents:

AWS Certified Security – Specialty Official Study Guide

AWS Organizations SCP Evaluation Logic

SCP Deny Precedence and Exception Patterns