HARRISBURG — Pennsylvania-based casino owner Penn National Gaming sued Tuesday in a challenge to a central element of the state’s aggressive new law expanding casino gambling.

In the lawsuit, filed in federal court in Harrisburg, Penn National Gaming said that provisions allowing 10 more mini-casinos would cause “significant and unique” harm to its suburban Harrisburg casino, Hollywood Casino.

Penn National said that the law, passed in October, effectively allows competing casino owners to use the new mini-casinos to pick off its relatively far-flung customer base, while the protections in the law are far more adequate for the rest of Pennsylvania’s casino owners.

“There was no rational basis for this arbitrary and inequitable treatment of (Penn National), which violated (its) constitutional rights in multiple ways,” the 57-page lawsuit said.

It said the bill violates its constitutional rights to equal protection and due process, as well as Pennsylvania’s constitutional prohibitions over legislation that benefits a particular person or entity.

Two other lawsuits filed in recent days, one by Las Vegas Sands and another by Penn National, target other aspects of the law.

The bill, a couple years in the making, won passage from lawmakers within 18 hours after it was unveiled despite opponents’ warnings that it carried unforeseen consequences and complaints that it contained sweetheart deals.

Alan Woinski, president of Gaming USA Corp., a New Jersey-based consultancy that publishes newsletters on the gambling industry, called the law “the worst gaming expansion bill in the history of the casino business” in a Monday newsletter.

Pennsylvania is the nation’s No. 2 state for commercial casino gross revenues, second to Nevada, and already rakes in more tax revenue from gambling than any other state.