The only way they could have been arrested legaly if there were on private property and were asked to leave but didn’t. Not enough info in the article, but from what I read it was on public land so this looks to not be the case.
The charges were disturbing the peace.
I don't care whether their literature was about Christianity, Tea Parties, Jenny Craig or Zoroastrianism. If they're just standing on a public sidewalk handing out literature, those who want it can say "Thank you" and those who don't can say "No, thank you."
Not "You're under arrest."
Perhaps the Dearborn cops don't know Jack Chick about the First Amendment.