(FORTUNE Magazine) – One of the strangest twists to the Sept. 11 tragedy is starting to unwind. It turns out that former World Trade Center occupants may still be obligated to pay rent on their office space. Language in numerous leases ensures that tenants can't break the covenant in the event of a disaster. And an "act of God" section--standard in many leases--states that they can't ask for rent reductions in the cases of "war or any matter...beyond the control of the [landlord]."

Why won't the landlord just break the lease? Well, that's sort of complicated. Larry Silverstein, the real estate mogul who led a group of investors in securing a 99-year lease on the World Trade Center in July, is still on the hook to the Port Authority of New York and New Jersey, the government agency that built the ten-million-square-foot complex. The Port Authority is demanding $116 million a year from Silverstein; his creditors are asking for another $180 million. Plus, Silverstein's lease requires him to rebuild the World Trade Center, a job that the state of New York recently estimated would cost $8.2 billion.

So far the 70-year-old millionaire isn't trying to collect rent from his tenants. "Silverstein is seeking to resolve all tenant rent issues in a fair and expeditious matter," says Howard Rubenstein, his spokesman. That, of course, may change. Experts say that as horrific as this disaster was, the World Trade Center leases are still enforceable and valid. "Just because he's not sending out invoices doesn't mean the rent isn't due," says M. Myers Mermel, CEO of TenantWise, an online real estate brokerage.

Perhaps Silverstein is waiting to see how his insurance claims pay out. When he signed the lease on the World Trade Center in July, he negotiated a $3.5 billion policy. Silverstein argues that his insurers owe him double damages--$7 billion--because the Sept. 11 attacks delivered him not one loss but two. His insurers don't seem convinced. One of them, Swiss Re, has filed a lawsuit disputing his claim.

Silverstein's argument may seem a reach, but so far he's winning the public relations war--and could very well win the court battle. If the case goes to trial, a New York City jury or judge might not sympathize with a Swiss company's attempts to lowball the insurance on the World Trade Center. Silverstein's tenants at the complex had better hope so. Otherwise, prepare for New York's latest drama: The Rentman Cometh.