Between 2011 and 2012, large, secret donations from the billionaire owner of one of America’s leading lead producers provided critical support to Wisconsin Governor Scott Walker and the Republican-led legislature as they weathered recall elections. Not coincidentally, around that time the lawmakers passed two laws that would effectively make it impossible for childhood victims of lead poisoning to sue lead companies, according to leaked documents obtained by The Guardian.

Since the laws were passed, federal courts have overturned key elements of them, ruling them unconstitutional and allowing legal challenges to go forward. However, if the laws had stayed in effect, they would have spared lead industries from potentially paying out millions in damages to hundreds of victims who were exposed to extremely high doses of the poisonous metal through paint during childhood.

“These children were perfectly innocent. They entered life with all the gifts and health that God gave them and were devastated by this neurotoxin,” Peter Earle, the principal attorney on 171 cases that are currently ongoing against lead producers and lead paint manufacturers, told The Guardian.

Lead was banned from household paints in the US in 1978, decades after the lead industry was aware of the toxicity of its product. The Centers for Disease Control and Prevention has since noted that there is no safe level of lead for children, in which the toxic metal causes learning and developmental disabilities. Lead blood levels of 5 micrograms per deciliter or higher are now considered concerning for kids—as was the case in many Flint, Michigan, children. Yet, one of the plaintiffs represented by Earle, named Yasmin Clark, had levels of 48 micrograms per deciliter as a child due to exposure to lead paint in her house in Milwaukee.

Under the two Wisconsin laws, Clark’s negligence suit would have been thrown out. The first of the laws, enacted in early 2011, required any new alleged victim to definitively prove that the company they were suing was responsible for making the exact paint that they inhaled or ingested at the time of their poisoning—basically an impossible feat given multiple paint layers within houses and exposures that occurred long ago in childhood. The second law, slipped into a 2013 budget bill at the last minute, made sure the rule applied not just to new lawsuits, but pending ones as well. Together, the laws would render lead producers and lead paint manufacturers effectively immune to all lawsuits.

According to the leaked documents—which were assembled during a state investigation into alleged campaign finance violations—the GOP got several key donations in between those two legislative moves. Harold Simmons, the billionaire owner of NL industries, a leading producer of lead previously used for lead paints, wrote three checks, totaling $750,000, during that time. The checks were made out to the Wisconsin Club for Growth, then run by one of Gov. Walker’s top advisors.

Simmons already had a reputation of getting off the hook for paying damages to lead poisoning victims and had gained notoriety in Texas for dumping toxic waste. The document also revealed that Walker’s advisors cautioned him about these “red flags.” However the warnings weren’t enough to keep the lawmakers from cashing Simmons’ checks.

In 2014, a federal court overturned parts of the laws, calling them unconstitutional, and reinstated lawsuits against lead companies.

Lead-based paint and lead-toting dust from crumbling paint remain the leading source of lead poisoning in the US. The CDC estimates that about 24 million homes in the country are contaminated, more than 4 million of which house one or more children.