A California lawmaker wants cellphone firms to report how often they release consumer location information to law enforcement officials, but the industry says it will fight the measure, according to a letter posted by the American Civil Liberties Union.

The California legislative proposal, which would form cellphone companies to make detailed reports available on the Internet, could have national implications, as it could be imitated by statehouses around the country. And any system implemented to accommodate that state's law could apply to many of the nation's consumers, any time they interact with California consumers.

The issue of local cops' getting detailed information from cellphone providers has garnered greater national attention this month, after the ACLU released the results of an extensive study.  More than 200 local police agencies shared details about their data-gathering habits in response to a series of Freedom of Information Act requests. In a special report, msnbc.com examined thousands of data request invoices received by the ACLU.

State Sen. Mark Leno, a Democrat, introduced legislation this year that would require mobile companies to publicly disclose the number of law enforcement location-related requests they receive annually. It would also prohibit disclosure of such information without a warrant — policies around the country vary.

The wireless industry trade group CTIA sent a letter to Leno on April 18 saying it opposes the legislation.

"The provider reporting requirements create unduly burdensome and costly mandates on providers and their employees and are unnecessary," said the letter, which was signed by Jamie Hastings, CTIA's vice president for External & State Affairs. "It is ... unclear what useful purpose such reports would serve. As wireless providers are constantly working to respond to ever-changing consumer demands, it is doubtful that diverting provider resources away from meeting these demands to comply with these reporting mandates would best serve wireless consumers."

The telecommunications group also said the warrant requirement may "create confusion" and "hamper (wireless firms') response to legitimate law enforcement investigations."

The ACLU, which says it wants to create wider public discussion on the issues surrounding cellphone location information, posted the CTIA letter on its website Monday. It criticized the trade group for opposing the legislation.

"Wireless companies should be doing everything in their power to protect the privacy of customer location information and making sure it cannot be misused, not opposing a crucial privacy bill that would ensure proper oversight for police access to the sensitive location data that these companies collect about us," Nicole Ozer, an ACLU policy director in California, wrote in a blog post on Monday.

She took issue with the industry's assertion that a reporting requirement would be burdensome, saying cellphone firms must already keep track of that data. She noted that the CTIA letter said telecom employees are "working day and night to assist law enforcement," and she said that was misguided.

"Our location data — where we go and what we do — is sensitive information. Wireless companies should be working day and night for us — their customers — not for law enforcement," she wrote.

In a follow-up statement to msnbc.com, the wireless industry association said its objection was chiefly with the additional reporting burden the law would place on cell phone firms, and not on the privacy rights issues. 

"There is a lot of misinformation on our position on California's mobile privacy bill," the trade group said in a statement, signed by Hastings. "While we are opposed to SB 1434, our opposition is focused on its provision that places reporting burdens on carriers rather than on the prosecutors who make these requests. ... Our opposition to (the legislation) in no way should be considered as a degradation of the wireless industry’s commitment to its customers' privacy."

Hastings also said that wireless carriers shouldn't have to be in the business of vetting the legality of cellphone records requests.

"It is up to the legislature and the courts to strike the appropriate balance between a citizen's privacy and law enforcement's legitimate need for information," Hastings' statement said. "While I want to be absolutely clear that our members are 100 percent committed to protecting our customers and their privacy, CTIA does not believe that wireless carriers should be expected to seek court review of the legality of the subpoenas and court orders they receive seeking location information."

Law enforcement use of wiretaps, location information and so called "pen trap and trace" data, which shows whom a caller is talking with, has increasingly become a controversial issue for privacy advocates. The ACLU report released April 2 offered the first glimpse of how often such data is used by local cops. Federal agencies are supposed to report annually how often they use such investigative techniques, but repeatedly, the Justice Department has failed to provide such reports to Congress, which was reported by Wired.com earlier this year.

There is precedent for disclosure of such data. Google voluntarily provides information about law enforcement requests on its "Transparency Report" website.

Stronger state laws are needed to provide a check and balance on police use of revealing mobile phone information, and annual reports would call attention to any sudden increase in use of the data.

"It’s time to update California privacy law so it matches our modern mobile world and keeps our personal information safe from misuse," Ozer wrote.

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