From your link - “Dearborn has never been, nor ever will be, under sharia law. We are governed by the U.S. Constitution, the Constitution of the State of Michigan and the City of Dearborn Charter,” said Mayor O’Reilly.
From wiki - The city's population includes 40,000 Arab Americans.[17] Ethnic Arabs own many shops and businesses, offering services in both English and Arabic.[18] In the 2010 census, Arab Americans comprised 40% of Dearborn's population; many have been in the city for several generations. The city has the largest proportion of Arab Americans in the United States.[19] As of 2006 Dearborn also has the largest Lebanese American population in the United States.[20] -and-As of the 2010 census the population of Dearborn was 98,153. The racial and ethnic composition was 89.1% Whites, 4.0% black or African-American, 0.2% Native American, 1.7% Asian, 0.2% Non-Hispanics of some other race, 4.0% reporting two or more races and 3.4% Hispanic or Latino.[13] 41.7% were of Arab ancestry (categorized as "White" in Census collection data).[14]
So I'm not so sure the statement made in your link can be made with absolute certainty.