aw enforcement officials have extensive powers to detain people when investigating attacks on the country, legal experts said yesterday.

The experts said the detentions in recent days of more than two dozen people on charges of immigration violations and six as material witnesses in Tuesday's terrorist attacks, showed that officials were using that wide latitude.

They are unlikely to be second- guessed by judges, several legal experts said. "No judge wants to be responsible for another act of terrorism," said E. Joshua Rosenkranz, president of the Brennan Center for Justice at New York University Law School.

Because the government controls who can enter the country, the powers of officials are especially expansive in dealing with immigrants. Judges in the past have permitted immigrants to be held on evidence kept secret even from the courts.

"We don't have preventive detention in our law for acts of terrorism," said Arthur C. Helton, an expert on immigration law who is a senior fellow at the Council on Foreign Relations. "That's why all these people are being held on immigration violations, because the discretion enjoyed by immigration officials is almost complete."

The United States Supreme Court has approved holding people in immigration cases, even as a pretext to pursue leads to other crimes.

Although not as expansive, the power of prosecutors over people defined as material witnesses is also very broad. Officials generally must obtain permission from a judge to hold someone as a material witness.

But lawyers say the anxieties across the country suggest that judges would be sympathetic to assertions of law enforcement officials. "It is highly unlikely under these circumstances that a judge would refuse to sign a warrant," said Thomas P. Puccio, a former federal prosecutor.

Under federal law, a person can be held as a material witness if there is probable cause to believe the person has information that could be important to an investigation and if it "is or may become impracticable" to assure that the person will be available to testify.

Defining people as material witnesses could be a short cut to detain people, said Aaron R. Marcu, a former federal prosecutor who is a defense lawyer at the law firm Covington & Burling. He said it would be much easier to show that a person had information than it would be to show that there was reason to believe the person was involved in the terror conspiracy.

And because there are international terror networks, it would not be difficult for prosecutors to assert that witnesses might flee, said Frederick P. Hafetz, another former federal prosecutor who is a defense lawyer in New York.