If so, that would appear to cross the line from simple information-gathering by people outside a company to sharing of potentially material information by employees who have a duty to keep it confidential.

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"Insider trading basically comes down to where you know or ought to know that the person from whom you're getting this information has a duty to someone else to keep it confidential, " said former Securities and Exchange Commissioner Paul Atkins in a video interview with The Wall Street Journal.

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While an NDA is an important legal contract that binds the signer to keep confidential information confidential, it typically does not provide clear guidance about how the signer should accomplish this responsibility.

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In late 2008, after the government came to its rescue, AIG managed to convince the Securities and Exchange Commission to keep the chart confidential. it relented in March 2009 and released the names of the 16 bank counterparties and their exposures but not the specific deal information.

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Personal data about staff can still be restricted, but it is harder for authorities to keep other material secret on the basis that it is confidential or threatens commercial interests than it would be in response to an FOI request.

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Before leaving, she made it clear that I must keep everything confidential, and that she had asked me to help mainly because she wanted the women to feel safe when they went out.

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Under a federal shield law introduced in 2011, the federal government would have had to prove to a judge that the information it was seeking outweighed the journalist's need to keep confidential information, according to the Society of Professional Journalists.

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Palmer's widow, Debbie Palmer, told the Times she would not break her promise to keep the contents of the tape confidential, but said she was in "awe" after hearing it.

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