Should a web-based non-modal dialog prevent users from leaving it via keyboard access?

Say that a dialog is non-modal, meaning that a user can use the mouse to interact with elements outside of the dialog without closing it.

Does this also mean that the user should also be able to interact with elements outside of the dialog using keyboard access, notably cycling through the elements via the Tab key?

I am looking for an authoritative source specifically addressing non-modal dialogs (not modal dialogs), especially if it relates to the web.