The U.S. Supreme Court on Monday struck down most of the state of Arizona's tough immigration law, but ruled that one of the more controversial elements of the statute could go forward.

The court upheld the requirement that state police officers with “reasonable suspicions” check the immigration status of people they stop for other reasons. However, they said the provision could be subject to additional legal challenges.

The justices rejected three other provisions of the Arizona law — ones that make it a crime for immigrants without work permits to seek employment; make it a crime for immigrants to fail to carry registration documents, and authorize the police to arrest any immigrant they believe to be deportable.

Five justices were in the majority to strike down the three provisions. The dissenting justices argued that the whole law should have been upheld.

Arizona's state legislature passed the law in 2010. State leaders said it was necessary to stem illegal immigration into the state, most of it coming from South and Central America. They say the federal government has failed to fully enforce national immigration laws.

Opponents, including Hispanic groups, argued that the law forces police officers to racially profile people. The Obama administration also argued that the U.S. Constitution places the responsibility for immigration in the hands of the federal, not state governments.

The court essentially agreed that immigration is a duty of the national government, not states.

The ruling follows an executive order signed by President Barack Obama earlier this month that halts the deportation of some young illegal immigrants.

Immigration is expected to be a significant issue in this year's elections, including the presidential race between Mr. Obama and the expected Republican candidate Mitt Romney.

On Monday, Mr. Romney used the ruling to denounce Mr. Obama for the lack of an immigration plan. He said every state “has the duty — and the right — to secure our borders” when the federal government “has failed to meet its responsibilities.”

The president said the ruling highlited the need for “comprehensive immigration reform.” He said he is “concerened about the paractical impact” of the provision that the justices upheld.

The growing Hispanic population in the United States has increasing voting power, and some political analysts say those voters could sway the election.

The Supreme Court on Monday also ruled states can not impose mandatory life-without-parole sentences on juveniles who are convicted of taking part in a murder.

The justices said states violate the constitutional ban on cruel and unusual punishment when they do not allow for the option of a shorter sentence.

The justices ruled 5-4 in that case.

The court also announced the decision on President Obama's health care overhaul probably will come Thursday.