LC Schedules are arranged by jurisdictions while religions span many jurisdictions which creates a problem since the LC schedule for Religious Law (including Islamic Law) is KB which has not yet been completely written.
The first schedule published in October 2001was KBR-KBU (History of Canon Law, Law of the Roman Catholic church, The Holy See).
Islamic Law is in KBP (published in 2004)
For religions not yet published approach the classification by jurisdiction. If two or three countries are mentioned use the most prominent one, if this is not possible try comparative as a possible solution.
Further reading on the problems with religious law is explained in this article. CATALOGING RELIGIOUS LAW / by Aaron W. Kuperman, Library of Congress (February 1995)