def is_subject_mutable(context, subject):
    """Return True if the subject is mutable in this context."""
    # Is admin == subject mutable
    if context.is_admin:
        return True

    # No owner == subject not mutable
    if subject['owner'] is None or context.owner is None:
        return False

    # Subject only mutable by its owner
    return subject['owner'] == context.owner