For Arizona sheriff Antonio Estrada, enforcing a state law that requires officers to determine the immigration status of people they stop and suspect are in the United States illegally was always going to be difficult.
But that is exactly what he will soon be expected to do now that the US Supreme Court has upheld the most controversial aspect of Arizona's crackdown on illegal immigrants.
"They are focusing on one particular group of people, Hispanics, and here along the border ... it can be pretty challenging to determine who's here legally and who isn't," said Estrada, the sheriff of Santa Cruz County, which flanks Mexico in southern Arizona.
He is among police chiefs throughout the state grappling with the practical aspects of just how to implement the law in a state where there are about 2 million Hispanics - nearly a third of the state's 6.5 million people - reside legally and an estimated 360,000 are there illegally, according to government figures.
The provision requires police to make a reasonable attempt to check the immigration status of people they stop, even for an offense such as jay walking, if they suspect that they are an illegal immigrant.
After the ruling, Arizona Governor Jan Brewer expressed confidence that law officers in the state would implement the law "efficiently, effectively and in harmony with the Constitution," and said civil rights would be protected and racial profiling would not be tolerated.
On Monday, Phoenix Police Chief Daniel Garcia sought to reassure residents that his officers would not discriminate on racial grounds. He told reporters he would not tolerate profiling and that the agency would continue to target violent and property crimes as a priority.
But for Estrada, in Santa Cruz County where more than 80 percent of the population is Latino and where many speak Spanish at home, requiring deputies to try to determine the status of those they arrest and suspect are undocumented presents challenges.
"If you are going to guide yourself by the colour and the language, you're going to be racially profiling, so you are going to have to avoid that," he said.
The measure is not expected to come into effect for at least two weeks while the restraining order placed on the law by a US District Court judge before it came into effect in July 2010 is modified.
Garcia, meanwhile, said that refresher training ordered by Brewer for police would not be completed for seven weeks.
Nevertheless, other police chiefs in Arizona are concerned that requiring officers to make a "reasonable" attempt to determine a suspect's status could lead to potentially ruinous litigation from both supporters and opponents of the law going forward.
"It's a fairly precarious position to be in, especially with the situation as gray as it is," said Jeffrey Smythe, the chief police in Show Low, a small city about 190 km east of Phoenix.
"One side's going to interpret your actions one way, the other side's going to interpret the exact same actions a different way, and both sides can sue us for that ... we could be on the hook for damages," he added.
Smythe said he was concerned that if "the litigation arena got bad enough for any given city you could almost bankrupt the city in some kind of ridiculous legal battle".
Hours after the ruling on Monday, the US Department of Homeland Security rescinded the authority a joint state-federal task force had given law enforcement agencies to enforce federal immigration laws, raising further doubts about how effectively police in the state can enforce the law.
Experts say the move throws into doubt co-operation between Arizona police and US Immigration and Customs Enforcement agents needed to implement the law.
"The impact (of the law) in Arizona in the short term is pretty insignificant, because it's pretty clear that ICE isn't going to respond to these calls," Grant Woods, a former Arizona Attorney general told a conference call with reporters on Tuesday.
"So, at least in the short term, I don't think anything's going to change."