Ubiquitin, I am not sure about that. In the case of the Good News Community Church of Gilbert, Arizona SCOTUS ruled that the town would have to show why an ordinance regulating signs was needed. There the sign was deliberately made to stand out. With an eruv only someone who knows that the lechis are there and why would notice – maybe (thus shuls put out eruv maps).
BTW, there is a story about a Reform group that challenged the eruv. The gentile judge asked the eruv committee’s lawyer how much it would cost the taxpayers. When he replied that the committee would be paying a fee to the municipality the judge told him to put up two. On the other hand, when the Prussian army entered Strasbourg during the Franco-Prussian War they took down the eruv because they thought that it was a communications wire. The rav of the city explained to the commander that when the Jews look at the wire they see a wall. He replied that the Jews can look at air and see a wire.