ANNAPOLIS, Md.—Maryland's highest court has struck down a crucial piece of a 17-year-old state law that immunized landlords from childhood injury claims stemming from lead paint exposure.

The state's Reduction of Lead Risk in Housing Act, enacted in 1994 chiefly to combat childhood brain injuries caused by lead poisoning in older rental apartments, shielded landlords from litigation if they could prove that they had taken certain statutory measures to mitigate the risk of exposure, court documents show.

Seven justices of the Maryland Court of Appeals ruled unanimously on Monday that the property owners' protection provision violates Maryland's constitutional guarantee of judicial remedy in personal injury cases. The ruling overturned two lower state courts, both of which held that the protection was valid because the lead paint law requires landlords to offer rent subsidies and relocation compensation to tenants in affected properties.

In the Maryland high court's written opinion, retired Justice John Eldridge—who was specially assigned to the case—wrote that landlords cannot claim immunity from liability because the lead paint law's remedy provisions for tenants and their injured children are “drastically inadequate.” The maximum payout under the law is $17,000, he noted, with $7,500 for medical treatments and $9,500 for relocation benefits, rent subsidy and incidental expenses, according to court documents.

“For a child who is found to be permanently brain damaged from ingesting lead paint, proximately caused by the landlord's negligence, the maximum amount of compensation under a qualified offer is minuscule,” Judge Eldridge wrote. “It is almost no compensation. Thus, the remedy which the act substitutes for a traditional personal injury action results in either no compensation or drastically inadequate compensation.”

Additionally, Judge Eldridge said the landlords' indemnity is not protected under state law that supports “traditional and well-established” grants of immunity.

The court's decision marks the culmination of a nine-year legal battle between a Baltimore mother and her landlords.

Tameka Jackson filed suit in a Baltimore Circuit Court in 2002 after her daughter, then-5-year-old ZiTashia Jackson, developed “severe and permanent brain damage” from ingesting lead paint in two apartments owned by Dackman Co., Jacob Dackman & Sons L.L.C. and Elliot Dackman. The suit alleged negligence and deceptive practices in violation of the state's Consumer Protection Act, as Ms. Jackson argued that the landlords told her that the first of two apartments she rented from them was “lead free.”

The ruling remanded the case to a lower state court.