PHOENIX -- Arizona cannot begin enforcing key parts of last year's immigration law.

In a split decision this morning, the 9th Circuit Court of Appeals concluded there was sufficient evidence to believe that provisions of SB 1070 are an unconstitutional infringement on the exclusive power of the federal government to regulate immigration. Judge Richard Paez, writing for the majority, also said such a conclusion is supported by ``the threat of 50 states layering their own immigration enforcement rules on top of the Immigration and Naturalization Act.''

The court specifically rejected the state's argument that it could make it a state crime for an undocumented worker to seek employment in Arizona. The judges noted that Congress, in approving federal regulations, chose not to make looking for work a criminal act.

Today's ruling upholds the decision issued last July by U.S. District Court Judge Susan Bolton. She agreed with the U.S. Department of Justice that Arizona was treading into legally forbidden waters.

It also is a major setback for Gov. Jan Brewer who took it upon herself to mount a defense of the law and, subsequently, to challenge Bolton's injunction. Brewer has solicited private funds and hired an outside counsel.

Senate President Russell Pearce, R-Mesa, who crafted the legislation, promised an appeal to the U.S. Supreme Court.

``There has never been a preemption against states enforcing these laws,'' he told Capitol Media Services. But Pearce said the decision is not a surprise.

``We expected -- almost could predict -- such a thing for the liberal makeup of the 9th Circuit, the most overturned court in the nation,'' he said.

The decision upholds the injunction against several sections of the law, including:

- Requiring a police officer to make a reasonable attempt to check the immigration status of those they have stopped;

- Forbidding police from releasing anyone they have arrested until that person's immigration status is determined;

- Making it a violation of Arizona law for anyone not a citizen to fail to carry federally issued documentation;

- Creating a new state crime for trying to secure work while not a legal resident;

- Allowing police to make warrantless arrests if there is a belief the person has committed an offense that allows them to be removed from the United States.

Paez said there is a role for states in enforcing federal immigration law. But he said it's not as broad as Pearce contends.

He cited laws which allow states to enter into agreement with federal agencies. But in those cases, Paez wrote, require the Attorney General to approve each individual state officer who is permitted to enforce that law but which functions each person is permitted to enforce.

Similarly, Paez rejected the state's argument that it has independent authority to enforce and punish violations of federal immigration registration rules.

And the court also concluded that there was no way Congress ever intended to allow undocumented workers who seek employment to be subject to criminal penalties, as does SB 1070. Pearce said that makes no sense.

``How do they know Congress didn't intend that?'' he said.

``They intended for (companies) not to employ these folks,'' Pearce continued. ``It's a felony to hire them. So it's a natural connection, a nexus, for that issue.''

Technically speaking, today's ruling does not determine the ultimate outcome of the challenge to the law brought by the Obama administration and others. It deals only with whether the law can be enforced while that case makes its way through the legal system.

But the conclusion by the appellate judges that SB 1070 is preempted by federal law, unless overturned, will make it next to impossible for Arizona to ever have the challenges overturned.

Today's decision could have implications far beyond Arizona. Several other states have enacted or are crafting laws modeled after SB 1070. If

The ruling was not unanimous. Judge Carlos Bea dissented, at least in part, saying there was evidence that Congress intended for states to help enforce some sections of federal immigration law.