The group tried to continue its adoption work in Illinois but, thanks to the new civil union law which allows gay and lesbian couples to be treated the way married couples are treated, it became impossible.
They have to even refer the unmarried couples which wanted to become parents to other agencies because of religious reasons, as they said.
The lawyers said that "the actions of the State have prevented the Charities from being able to obtain relief from the Illinois court system."
Anthony Martinez of The Civil Rights Agenda, gay rights group, said: "Finding a loving home for the thousands of children in the foster/adoption system should be the priority, not trying to exclude people based on religious dogma.
Dropping this suit is a step in the right direction for what is best for all the citizens of this great state."