Attaching multiple policies for S3

Question

Multiple IAM policies can be attached to the same IAM user. In one of the policies, let’s say the user is given access to a S3 Bucket and in another policy the user is denied to the same S3 Bucket. What is the net effect of attaching two policies to the same user in this case?

Answer 1

As per the AWS documentation here, an explicit deny takes precedence over explicit allow. So, in this case the net effect the user is denied access to the S3 Bucket. This is how the AWS IAM policies are evaluated.