By default, anyone with admin access to a repository can invite outside collaborators to work on the repository. You can choose to restrict the ability to add outside collaborators to organization owners only.
Note: Only organizations that use GitHub Enterprise Cloud can restrict the ability to invite outside collaborators to organization owners. 有关如何免费试用 GitHub Enterprise Cloud 的详细信息，请参阅“设置 GitHub Enterprise Cloud 的试用版”。
If your organization is owned by an enterprise account, you may not be able to configure this setting for your organization, if an enterprise owner has set a policy at the enterprise level. For more information, see "Enforcing repository management policies in your enterprise"."
在 GitHub.com 的右上角，单击你的个人资料照片，然后单击“你的组织”。
In the "Access" section of the sidebar, click Member privileges.
Under "Repository outside collaborators", deselect Allow repository administrators to invite outside collaborators to repositories for this organization.