http://www.thefreelibrary.com/Stock+buybacks%3A+the+rules-a054636937

TIMING STOCK PURCHASES

Even if a board of directors authorizes the immediate launch of a buyback program, the rules covering the timing of purchases around major developments within the company may cause the CFO See Chief Financial Officer. to delay implementing it. "We advise the company not to conduct a program at all if there is any material inside information that the company is aware of that has not been publicly disclosed," says Jayne M. Donegan, a corporate and securities-law attorney with Brown, Rudnick, Freed & Gesmer in Providence, Rhode Island

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..... Click the link for more information.. "For example, if the company is in merger negotiations or it knows the earnings but those earnings haven't been released, the company should not be out purchasing its stock."

To address potential insider trading, many companies inform their brokers that they may be required to suspend on short notice purchases authorized au·thor·ize
tr.v. au·thor·ized, au·thor·iz·ing, au·thor·iz·es
1. To grant authority or power to.

2. To give permission for; sanction: as part of an ongoing repurchase program. In fact, many companies apply the same "blackout period Blackout Period

1. A term that refers to a temporary period in which access is limited or denied.

2. A period of around 60 days during which employees of a company with a retirement or investment plan cannot modify their plans. "--forbidding all trades--to corporate repurchasesCorporate repurchase

Active buying by a corporation of its own stock in the marketplace. Reasons for repurchase include putting idle cash to use, raising EPS, creating support for a stock price, increasing internal control (shark repellant), or stock for ESOP or pension plans.
..... Click the link for more information. as they do for insider stock purchases by individuals. For example, a company may decide not to trade during a period that extends from 10 days before through two days after any earnings release.

Assuming no pending developments prevent a buyback and the company's legal counsel gives its blessing, the next step for the executive administering the program is to get board authorization for it. That authorization should state both a dollar or share purchase limit and a time frame--for example; $5 million over one year, 3% of shares outstanding over the next six months or a half million shares before year-end. After the board makes its decision, the company should issue a press release detailing the program.''