The Rebbe on Publicizing an Eruv in a Large City
An eruv can be checked before Shabbos and fail later. The Rebbe was concerned that the permission would be publicized widely, while news of a broken wire, changed wall, or withdrawn heter would reach only part of the same public.
The original announcement outlives the later warning
In a letter to Rabbi Yosef Dovid Moskowitz (Rosh Chodesh Adar 5718), the Rebbe writes against announcing the completion of a city eruv. The eruv may later become invalid, yet the original announcement remains in people's minds.
A correction rarely travels as far as permission. People who have seen observant families carry for months or years may never hear that a section failed or that the psak changed. The Rebbe treated that foreseeable result as part of the decision whether to publicize the eruv in the first place.
“On condition that it not be publicized at all”
The typed response published by Rabbi Sholom Dovber Levin says that eruvin “frequently become damaged”, that notice reaches only a minority, and that few people stop carrying once they have become accustomed to it.
It then says that in a place with no reshus harabim de'oraisa which is otherwise suitable for an eruv, making one can be worthwhile “on condition that it not be publicized at all.” The response is describing a discreet protective eruv in a place already fit for one, not using secrecy to overcome a reshus harabim or an invalid boundary.
The Melbourne proposal
When Rabbi Yitzchok Dovid Groner asked about a proposed Melbourne eruv, the Rebbe answered that his view was known and called for a thorough investigation by qualified local Rabbonim. The conclusion was that an eruv should be established only in secrecy (5 Iyar 5741).
Rabbi Yonason Johnson, writing from Melbourne decades later, rejected the suggestion that this concern was only about government permission to make repairs. He understood the warning to apply even to a carefully built eruv: one invalid Shabbos after carrying has become normal is enough to create the feared failure.
The publicized route in Crown Heights
The Crown Heights route was announced publicly as an eruv even though the neighborhood Beis Din did not accept it. Maps and weekly status notices teach permission more quickly than the halachic objections reach someone encountering the subject for the first time.
The local ruling therefore states the practical position without qualifications: the publicized eruv is treated as nonexistent, and carrying remains prohibited.