SPRINGFIELD — The Illinois State Rifle Association and eight gun businesses sued the state Wednesday, seeking to block a law that requires gun retailers to be licensed by a federal agency then certified by the state.The complaint filed in Sangamon County argues the new law is vague and unnecessary, ISRA Executive Director Richard Pearson said.Under the law, signed by Gov. J.B. Pritzker after taking office in January, gun dealers are required to certify their federal license with the Illinois State Police.It also …