PHOENIX - As America's busiest immigrant-smuggling hub, Arizona is considering a tough proposal that would make it the only state to criminalize illegal immigration through an expansion of its trespassing law.

If the Legislature and governor approve the proposal, state law would draw local authorities deeper into immigration enforcement in defiance of the notion that immigration is the sole responsibility of the federal government.

The proposal, which has cleared the state Senate and is being considered by the House, would require police to try to determine people's immigration status when they have reasonable suspicions that a person doesn't have legal status. Violations would bring jail terms.

While the practical effect of such a law is still unclear, advocates of immigrant rights predict it would lead to racial profiling that would target thousands of Latinos who are U.S. citizens. Some question the proposal's constitutionality.

A few years ago, police chiefs in two communities in New Hampshire charged illegal immigrants with trespassing for being in the state. A local judge in 2005 dismissed the charges as an unconstitutional attempt to apply state laws to a federal issue.

Backers of the Arizona proposal say that on top of inadequate federal border efforts, many local police departments have turned a blind eye to illegal immigrants.

Some politicians "don't have the courage to stand up for their citizens," said State Sen. Russell Pearce of Mesa, the bill's sponsor.

The measure cleared the Senate on a 16-12 vote last Monday and is being considered by the House. The proposed trespassing provision is similar to proposals vetoed in 2006 by then-Gov. Janet Napolitano, who said she opposed turning all illegal immigrants into criminals.

Republican Jan Brewer, former secretary of state for Arizona, became governor in January upon the resignation of Democrat Napolitano, who quit to head the Homeland Security Department in the Obama administration.

Under this year's proposed trespassing provision, a first offense would be a top-tier misdemeanor punishable by up to six months in jail. Subsequent violations would be a felony that could carry up to 21/2 years in prison.

Agencies arresting first-time offenders would have the option of prosecuting them or turning them over to federal authorities.

Supporters say the measure would not encourage racial profiling, because officers would still need probable cause to believe that people violated the law before they could arrest them.

Opponents say officers who are not schooled in the complexities of immigration law would likely approach people based solely on appearance.

"It's almost impossible for it to be applied without relying on racial profiling and without committing egregious errors," said Jennifer Allen, director of the Border Action Network, an immigrant-rights group based in southern Arizona.

And communities could be stuck with legal bills from any mistakes made by officers who are not trained in immigration law, said Robert DeVries, who is chief of police in the western Arizona town of Kingman and president of the Arizona Association of Chiefs of Police.