The problem is that the law does not define "sexually explicit materials," the Chicago Tribune reports. Most bookstore owners say that they have works on their shelves that might qualify.

Philip Schatz, an owner of Erasmus Books in South Bend, said that the store carries pretty much what the public library does.

"We have books someone could find objectionable in our psychology section, or our art section, or our gay and lesbian section," he said.

The law applies only to new businesses or those that relocate, requiring them to pay a $250 fee. State Rep. Terry Goodin, a Democrat from southern Indiana, sponsored the measure after an adult bookstore opened in his district. The owner allegedly misled neighbors on what type of business was planned.

Daniel Conkle, a law professor at the University of Indiana, suggested the law is too vague to be enforceable.

"This law is kind of a blunderbuss," he said.