North Dakota has become the second state in the US to ban the forced implanting of radio frequency identification (RFID) chips in people.

The two-sentence bill, passed by the state legislature, was signed into law by Governor John Hoeven last Week. Essentially, it forbids anyone from compelling someone else to have an RFID chip injected into their skin. The state follows in the steps of Wisconsin, which passed similar legislation last year.

"We need to strike a balance as we continue to develop this technology between what it can do and our civil liberties, our right to privacy," Hoeven said. He emphasised that the law does not prohibit voluntary chipping. Military personnel who want an RFID chip injected so they can be more easily tracked will still be allowed to get a chip. There are also potential uses for the technology in corrections or in monitoring animals, he noted.

Marlin Schneider, the state legislator who sponsored the Wisconsin law, said he is glad to see an anti-chipping legislation trend. However, such statutes do not go far enough to curb the ability of private sector retailers and manufacturers to "implant these things into everything we buy."

Ultimately, with RFID tagging systems, corporations "will be able to monitor everything we buy, everywhere we go and, perhaps as these technologies develop, everything we say," Schneider said.

But Michael Shamos, a professor who specialises in security issues at a US university, Carnegie Mellon, thought the law was too vague to do much good. For instance, it only addresses situations where a chip is injected, even though RFID tags can also be swallowed. And it does not clearly define what a forced implant is; someone could make chipping a requirement for a financial reward.

"Suppose I offer to pay you $10,000 (£5000) if you have an RFID [chip] implanted?" he asked. "Is that 'requiring' if it's totally voluntary on your part?"

The idea behind the law is not bad, but "it looks hastily drawn and will have unpredictable consequences," said Shamos.

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