There&#x27;s actually not.  Unless it infringes on a protected class (eg &quot;no black people&quot;) or a fundamental liberty interest, the &quot;rational basis&quot; standard prevails.  This basically means that if a hypothetical reason could be articulated to support a public interest it&#x27;s legal, even if it does not actually achieve that goal in practice.<p>This becomes particularly broad when you&#x27;re talking about actions in public.  So while it would probably be considered an intrusion to send the Dental Police into everyone&#x27;s home to be sure that they floss daily, it would probably be legal to have the Dental Police perform mandatory tooth-brushings on all taxi drivers.  Nobody is forcing you to be a taxi driver and you could reasonably avoid the situation by practicing another profession instead.<p>That&#x27;s how you get stuff like requiring hair nets for food safety.  But again, it doesn&#x27;t necessarily have to be sensical.  Unless otherwise restricted, states and cities have an enormous amount of leeway to do whatever they think is in their citizens&#x27; best interests.  It&#x27;s a list of things you <i>can&#x27;t</i> do, not a list of things you <i>can</i>.<p>If Austin wants to fingerprint taxi drivers, that&#x27;s well within their powers.  Not even controversial - that has been common practice for probably a half century now.