The Occupy movement's national call to action Tuesday – occupying foreclosed homes in at least 20 cities from New York to Los Angeles – seems guaranteed to expand the legal tussles that have dogged Occupy almost since its inception.

First Amendment speech is clearly protected in public places, legal experts say, but laws about the right to protest on private property are much less forgiving, meaning the new Occupy action will court a much harsher response from legal authorities.

For activists, the tactic is a powerful way to take on banks, which are unfairly foreclosing on homeowners, they say. But a ramping up of legal action against Occupy could sap the movement of money and energy, some experts say, and potentially alienate Americans by casting the protesters as law-breakers.

“You can speak your mind on a public sidewalk or roadway in front of a person’s home,” says Timothy Zick, a law professor at the College of William and Mary in Williamsburg, Va. “But you don’t have the right to do so on their property.”

Scuffles with the law have followed the Occupy Wall Street movement almost from its inception, when some 700 New York protesters were arrested on the Brooklyn Bridge in September. Since then, as tent encampments have been razed and arrests have multiplied, legal challenges have steadily mounted on both sides, with lawyers for the activists filing temporary restraining orders and mayors ordering police crackdowns.

But protesters in Tuesday’s anti-foreclosure day of action say they are not doing it to be arrested. Instead, they want to spotlight what Minneapolis organizer Anthony Newby calls a critical situation. “We are hoping to create a national movement to defend against illegal foreclosure,” he says, suggesting that banks have not been forthright in foreclosure proceedings.

Neither Bank of America or JPMorgan Chase – two of the nation’s largest retail banks – responded to a request for comment on Tuesday’s call to action.

Mr. Newby is working with a former Marine, Bobby Hull, who was foreclosed upon by Bank of America, who in turn sold the house at auction. Mr. Hull faces eviction by mid-February.

“We are not looking for a confrontation, but rather are trying to negotiate a peaceful solution,” says Newby. But if it comes to legal force, “we are prepared to defend Bobby’s home.”

He says that could involve hundreds of neighbors occupying the Hull home, possibly forcing law enforcement to move against all of them. “We are hoping the local police, who we think are part of the 99 percent, too, won’t take part in such actions against Bobby,” he adds.

To Peggy Mears, a Riverside, Calif., activist working with a local family to reoccupy their foreclosed home, the banks aren't holding up their end of the bargain. “The banks were bailed out, and they were supposed to use that money to help homeowners, but they have not,” she says.

The phone message at the Los Angeles chapter for the National Lawyer’s Guild seems to acknowledge the prospect of increased arrests. It tells any member of the Occupy Los Angeles movement: “We accept all collect calls from jail.”

But for the guild, jail “is not our goal, either,” says Executive Director James Lafferty. As a human rights bar association that facilitates public demonstrations, the job of the guild “is to use the courts to keep people in the streets.”

While legal decisions such as Roe v. Wade or Brown v. the Board of Education can make a difference, “the pressure that led up to those decisions came from people protesting in the streets,” he adds.

Indeed, extended legal struggles are not necessarily a desirable outcome for Occupy. They can drain money and momentum crucial to the long-term viability of any movement. If confrontations go too far, “they can also turn the public off to the movement," says University of Nebraska law professor Rick Duncan. "Who is going to be sympathetic to people who are obviously breaking the law by trespassing on private property?”

Implicit in the new Occupy struggle, however, are concerns about the loss of public space in which to protest, says Greg Magarian, a constitutional law expert at Washington University in St. Louis. “The privatization of public spaces where people can be seen and heard is a very dangerous shift,” he says.

He points to the origins of the Occupy Wall Street movement in the privately owned Zuccotti Park in New York City: “Whoever chose that park understood the importance of that symbol."