How can I suppress a type of items (legislation specifically) from showing up in bibliography, as MLZ does to "classic" automatically?

I've been using the following code in twlaw:
<layout locale="zh" suffix="。">
<choose>
<if type="legislation"/>
<else-if match="any" type="treaty" variable="jurisdiction">
<text macro="jurisdiction-filter-zh"/>
</else-if>
<else>
<text macro="tw-secondary-first"/>
</else>
</choose>
</layout>
but never tested it. Realized just now that it wouldn't work. MLZ gives me the following error message if a statute is cited:

[CSL STYLE ERROR: reference with no printed form.]