But Miller said the regulations may "overdramatize" the amount of criminal buying in luxury real estate. He said many celebrities, Wall Streeters and top executives often legitimately use LLCs to protect their privacy and give them legal protections.
What's more, title insurance companies may opt out of handling transactions in which they can't legally determine the true owner of an LLC, which can often be hidden by shell companies upon shell companies.
"The rules are a somewhat overzealous effort to go after a certain number of individuals but the whole space becomes tainted," he said.
Not all brokers and real estate companies said the rules will have a big impact.
"If maybe five or 10 bad guys are prevented from buying apartments in New York City, what's the big deal?" one real estate executive said. "It's not going to affect the market, which right now is very strong."
Although the luxury real estate market remained solid in the fourth quarter, analysts say falling stock markets and slowing growth overseas could put a chill on sales in 2016. Treasury's new rules also add a wrinkle of uncertainty.
"The market is strong right now," Miller said. "But these new rules can be unsettling."