When using the DocumentObj 2.5 Update API call I've found I can update objects that are a part of a frozen baseline, so long as an output has not been released for that baseline (or any baseline where the object is a member). The update can be of any type including changes to content.

When working in Pub Manager, though I can change some aspects of an object that is part of a frozen baseline, such as metadata and workflow status, I cannot check the object out and change its content, regardless of whether an output has been released. 

Also, if I try to use the API call to update a member of a frozen baseline, with output released, the error returned by the API call is to the effect of 'cannot perform the action because the object is part of a frozen baseline." Which kind of suggests that being a member of a frozen baseline should be enough to prevent it being updated, though in reality it must also be part of a released output.

So my question is whether this is expected behavior when using the API and if there any best practices around using the API to update objects while preventing changes to objects in frozen baselines.