From b2evolution manual

This manual page is outdated. NEW PAGE: User Permissions in b2evolution v5+.

User permissions get derived from three things:

• The General application settings. For example, whether or not to disable File Upload for everyone.
• The permissions of the user Group the user belongs to.
• The permissions of the blog the user is trying to access. Note: blog permissions can be assigned to specific users individually or to groups of users.

[edit] User Levels

See page about User levels