Curtis Bramble alerted federal agents about a mass gathering of undocumented workers at the state Capitol last winter — but the agency charged with enforcing immigration law didn't show up.

Study of this scenario illustrates the daunting complexity in the arena of enforcing immigration law.

"What he was asking us to do was to go down there and racially profile the people who were there," said Sid Siders, a special agent for the U.S. Immigration and Customs Enforcement.

The incident also underscores a new focus by officials of ICE, formerly Immigration and Naturalization Service, and the federal prosecutors who take illegal residents to trial.

During the last legislative session, Bramble, a Republican state senator from Provo, sponsored a controversial bill that gave illegal immigrants driving privilege cards and repealed a law allowing a temporary tax identification number to be used to obtain a Utah driver's license.

About 1,500 protesters took over the Capitol one day when the bill came before lawmakers.

Bramble presumed most of the demonstrators were in the United States illegally. Likely many were.

The senator says now his goal was not to "set up the paddy wagons and drag them away."

"I believed that if it were illegal aliens that were protesting and if the federal agency had a visible presence, it would have a tempering effect on the nature of the protest. That's all," Bramble said. "It was not meant to be heavy-handed to ID and deport or those types of activities."

But ICE officials did not attend the protest.

Instead, they spent that day chasing drug runners, human smugglers, hostage takers, document forgers and those committing marriage fraud and other crimes.

"Our goal is to pick off people much higher on the food chain," said Virginia Kice, an ICE spokeswoman based in Laguna Niguel, Calif.

This statement seems to belie facts about the presence of undocumented workers in Utah.

There are an estimated 85,000 undocumented immigrants in Utah. It is a felony for each one to be here.

But officials say there are limited resources and limited jail cells, and every Spanish-speaking Latino is not an illegal resident.

"People have a misunderstanding about what we do," Siders said.

Immigration enforcement breaks into several parts.

Local police who come across some people in routine traffic stops and learn they're here illegally can hold them for federal immigration officials.

These people go to a special immigration court — or federal court if they are suspected felons.

Federal agents investigate and locate people who have ditched immigration court proceedings or who have committed crimes.