Hewlett-Packard telephone taps

I'm curious, but how is this legal? The New York Times' Damon Darlin ("H.P. Spied on Directors to Find Leak") reports that HP's chairwoman, Patricia C. Dunn, "authorized" a team of "independent electronic-security experts" to monitor the private phone calls of HP directors to catch who had made leaks to the press that resulted in the ouster of HP's CEO, Carleton S. Fiorina. Turns out there were two leakers, Thomas J. Perkins (founder of the venture capital firm Kleiner Perkins Caufield & Byers), and George A. Keyworth II, the company’s longest-serving director. Perkins resigned, but Keyworth, who apparently didn't get to be the longest-serving director without some cajones, told the board to f-off, since he was elected by the shareholders, not them. This story only came to light because Perkins, after resigning, apparently later decided he was resigning because of a "disagreement" with the board, which, under SEC rules, forces the company to disclose the nature of the disagreement. (Good to see that Perkins managed to grow a set of his own cajones, at least after a while.)

My question is: how is it legal for a corporate chairperson to "authorize" the monitoring of someone's home telephone and cell phones? If the government did that, you'd need warrant. Just to get the phone records, you'd need a subpoena. But apparently, "H.P. said its legal counsel had advised her that the surveillance was legal and proper. "

Huh.