Why was I told 在什么情况下……吗？ is wrong? Under what circumstances can police use tear gas?

I translate it as

在什么情况下警察可以使用电击枪吗？

Someone told me this is not correct because it shouldn't end with 吗. But I don't understand, if can police use tear gas can be translated as 警察可以使用电击枪吗? then why can't the given example?
Should the statement &quot;Under what circumstances&quot;, when featured in a question, also include 吗 ?
“吗” is used in &quot;Yes-no questions&quot;, which are question that can be answered by &quot;yes&quot; or &quot;no&quot;.
With &quot;Under what circumstances&quot;/&quot;在什么情况下&quot;, the question cannot be answered by &quot;yes&quot; nor &quot;no&quot;. So &quot;吗&quot; should not be used.