A few weeks after Los Angeles threw in the towel on a plan to move its police force onto Google’s cloud-based email platform, Pittsburgh announced that it had shifted 3,000 employees -- including city cops -- to the cloud.

It took just four months and stayed within budget, Pittsburgh Mayor Luke Ravenstahl said at a January press conference that featured him and Google executives dumping an old city email server into a recycle bin. The city says the move will cut annual email costs by 25 percent and employees will get 500 times more email storage.

Contrast Pittsburgh’s experience with L.A.’s announcement that it was scrapping plans to move 13,000 city police officers onto its Gmail system due to unresolved security and privacy concerns. In 2009, the $7.2 million deal was considered groundbreaking because it envisioned moving email for all 30,000 city employees offsite and onto Google’s government cloud. The December decision means that almost half of the city workforce will stay on the existing -- and very old -- city-run email system, with Google paying $350,000 annually to keep it running, says the Los Angeles Times.

So why can one city police department make the leap while another can’t?

I suspect there are a few issues at play, including politics, workers’ resistance to change and perhaps an incomplete understanding among cloud vendors of the rules that public safety agencies must follow. But the biggest hurdle to moving cops onto the cloud may be that many federal, state and local rules on the privacy and security of police data were written before the advent of cloud computing.

L.A. CTO Randi Levin said as much in October. “The real issue is the fact that the policies related to a lot of different areas in government are not matching the technologies that are coming out,” she told Governing’s sister publication Government Technology.

The relationship between Google and the city started unraveling sometime toward the end of 2011 when Levin asked the project’s integrator to refund money spent trying to move police and justice personnel to Google’s system. She told media outlets that Google hadn’t met security and storage mandates tied to use of data from the FBI’s Criminal Justice Information Services Division, which lets local police access the federal storehouse of fingerprints and criminal histories. But Google claimed the city introduced new security requirements after the contract was signed.

Either way, until policies are clarified, cloud computing’s compatibility with law enforcement data will be open to interpretation -- and L.A. won’t be the only city struggling. Privately, many police department CIOs say they’re reluctant to move their data to the cloud, and they grumble that cloud vendors haven’t met special public safety requirements. On the other hand, Google says several cities, including Des Moines and Orlando, already have transitioned successfully.

Pittsburgh appears to be another one of those cities. Officials there are satisfied the system meets police needs. In interviews after the announcement, Pittsburgh’s then-CIO Howard Stern cited Google’s federal security certification and said the company’s security capabilities exceeded what the city could do on its own.

Google Vice President Michael Lock, who attended the Pittsburgh announcement, pointed to the cloud as a way for cash-strapped cities to upgrade their technology. “This is a shining example of what city, state and national governments need to do,” he said.

For some cities, that may very well be true. But for jurisdictions contemplating a similar move, the best advice may be to study those privacy and security rules, and to talk to your lawyers.