def tags_list_to_string(tags):
    """
    Given a list of ``tags``, turn it into the canonical string representation
    (space-delimited, enclosing tags containing spaces in double brackets).
    """
    tag_string_list = []
    for tag in tags:
        if ' ' in tag:
            tag = '[[%s]]' % tag
        tag_string_list.append(tag)
    return u' '.join(tag_string_list)