The answer is that the SCP implicitly denies EC2 because it uses an allow list that does not include EC2. This occurs because the SCP applies a default deny to all services not explicitly allowed, acting as an overarching permission boundary that overrides any account-level IAM policies, including one that explicitly allows ec2:RunInstances. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of how SCPs function as guardrails within AWS Organizations—specifically that an allow list SCP blocks all unlisted services, regardless of IAM permissions. A common trap is assuming an explicit IAM allow can bypass an SCP that lacks an explicit deny; in reality, an SCP’s implicit deny is absolute. Remember the memory tip: “SCP allow list = all else denied; IAM can’t override the guardrail.”
SAP-C02 Practice Question: Design Solutions for Organizational Complexity
This SAP-C02 practice question tests your understanding of design solutions for organizational complexity. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A large financial services company uses AWS Organizations with over 200 accounts. The security team has implemented a Service Control Policy (SCP) that denies access to all services except a whitelist that includes Amazon S3, Amazon DynamoDB, AWS Lambda, and Amazon CloudWatch. Recently, the DevOps team reported that they cannot create new EC2 instances in their development account, even though the administrator explicitly attached an IAM policy allowing ec2:RunInstances. The SCP does not explicitly deny EC2. What is the most likely cause of this issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The SCP denies all services not explicitly allowed, and EC2 is not on the whitelist
The SCP uses a deny-all approach with a whitelist of allowed services. Since EC2 is not on that whitelist, the SCP implicitly denies all EC2 actions, overriding any IAM policy that explicitly allows ec2:RunInstances. SCPs act as a guardrail that cannot be bypassed by account-level IAM policies.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The IAM role used by the DevOps team has a trust policy that does not allow EC2 actions
Why it's wrong here
The trust policy determines who can assume the role, not what actions are allowed.
✗
The EC2 service has been disabled via AWS Config in that account
Why it's wrong here
AWS Config is a compliance service, not a permission enforcement service.
✗
The development account is in an organizational unit (OU) with a different SCP that denies EC2
Why it's wrong here
The scenario states the SCP does not explicitly deny EC2.
✓
The SCP denies all services not explicitly allowed, and EC2 is not on the whitelist
Why this is correct
SCPs that use an allow list deny all services not explicitly listed.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think an explicit IAM allow can override an SCP, but SCPs set the maximum permissions boundary, so any action not explicitly allowed by the SCP is implicitly denied.
Trap categories for this question
Scenario analysis trap
The scenario states the SCP does not explicitly deny EC2.
Detailed technical explanation
How to think about this question
SCPs use an implicit deny model: if an action is not explicitly allowed by an SCP, it is denied, regardless of IAM policies. This is because AWS evaluates SCPs before IAM policies, and an SCP deny (including implicit deny) overrides any IAM allow. In this case, the SCP's whitelist acts as an explicit allow for listed services and an implicit deny for all others, including EC2.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Design Solutions for Organizational Complexity — This question tests Design Solutions for Organizational Complexity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The SCP denies all services not explicitly allowed, and EC2 is not on the whitelist — The SCP uses a deny-all approach with a whitelist of allowed services. Since EC2 is not on that whitelist, the SCP implicitly denies all EC2 actions, overriding any IAM policy that explicitly allows ec2:RunInstances. SCPs act as a guardrail that cannot be bypassed by account-level IAM policies.
What should I do if I get this SAP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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