Dann Grillo’s disability-discrimination complaint against his former employer, the Metropolitan Water Reclamation District of Greater Chicago, alleged an equal protection violation — based on the U.S. Constitution’s 14th Amendment and the enforcement mechanism provided by Section 1983 of the Civil Rights Act of 1871 — plus a violation of the Americans with Disabilities Act of 1990. But the water reclamation district countered with a motion to dismiss the Section 1983 claim based on Grey v. Wilburn …