That might sound like this case, in which an Arab Christian group sued over an anti-leafleting rule at the Arab International Festival on Dearborn (Michigan) city property. But the new case involves Christians who specialize in proselytizing to Jews; who allege that they were barred from leafleting and otherwise speaking in publicly accessible public streets — i.e., not just those portions that were blocked off for ticket-only access during the festival — at or near the Arts, Beats & Eats festivals in Pontiac, Michigan.
My analysis remains much the same as it was with the earlier incident: If indeed the plaintiffs were trying to speak or leaflet on public sidewalks that were generally open to the public, and if the police barred them from doing so either (1) because of the content of the speech, or (2) simply because they were leafleting or trying to speak to passersby (as opposed to, for instance, standing in a place where their leafleting or speech blocked pedestrian traffic), that would be unconstitutional.
The matter would be different if some group were putting on its own rally or some such, even in a public park or a public square, and got a permit that would let only its own members or invitees on the property on which the group itself spoke. In such a situation, the property could in effect be temporarily privatized, so that the group could express its own views without the interference of others. That, for instance, is why parade organizers (who have a valid parade license) are free to select who can participate in the parade, even though the parade proceeds down a city street.
But if the speech was in places which were open to public access, then the sidewalk remains a traditional public forum or at worst (from the plaintiff-speakers’ perspective) a nonpublic forum. Leafleting is generally constitutionally protected in both classes of forum. See Parks v. City of Columbus, a case from the federal circuit (the Sixth) in which the event took place.
Of course, all this depends on what actually happened (hence all the ifs); the city denies much of what the plaintiffs allege.
UPDATE: I originally described the group as Jews for Jesus, but a commenter pointed out that this is a different group of Christians who are trying to convert Jews; I have revised the post accordingly.