Block public access for functions [AWS Organizations]

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**Description**
We are exploring supporting Organization level policies to specify whether to block the attachment of new policies that would allow public access and/or restrict access to functions that are currently publicly accessible.

**Additional context**
1. What level of granularity do you need in an Organization level policy, for example, block access for all resources except this resource type?

The issue concerns AWS Organizations policies governing public access to Lambda functions, but it names no repository files, tests, or entry points. Start by reviewing the requested policy granularity and the two proposed behaviors: blocking new public-access policies and restricting currently public functions. Done would require a defined, agreed organization-level policy design.

Written by the indexing model from the issue text.