&gt;<i>Was that ever illegal? The license plates are publicly displayed and visible</i><p>Well, you are also publicly visible when you walk around the town, but police following you around all the time without a reason&#x2F;warrant is illegal (at least that&#x27;s the case in my country, it should be in yours too if it&#x27;s not).<p>Second, something being &quot;publicly displayed&quot; and &quot;allowed to be scanned automatically by government (or another party), catalogued and stored for millions of people&quot; is not the same thing.<p>&gt;<i>The only thing that changes is the economics of making it automated, no?</i><p>No, it&#x27;s the &quot;mass surveillance of citizens whereabouts&quot; that&#x27;s the illegal part that is&#x2F;should be illegal. Even if it was to be performed manually by people.<p>Now, one could say that it&#x27;s just the &quot;economics&quot; that changes, but beyond that, the economics are also an enabler. If it wasn&#x27;t for automated scanning it would impractical to even do it, so what changes is the very possibility of this happening.<p>One didn&#x27;t need to make non-automated license plate scanning illegal because it wasn&#x27;t practical to perform it in the first place.<p>Sure, it could happen at low scale, with &quot;spies&quot; manually writing e.g. all the plates parked in an area, or whenever a particular car passes from a particular street. But it wasn&#x27;t practical or widespread enough to make sense to single out and ban as a practice. The law is not an absolute affair.