Wall Street attorney Martin Lipton, known as the go-to guy for companies defending themselves against activist investors, has suggested that the balance of power may have tipped toward his long-time adversaries.

Lipton’s firm Wachtell, Lipton, Rosen & Katz last year advised more companies against activists than any other law firm, according to the WSJ-FactSet Activism Scorecard. But in a memo to clients that was posted online on Thursday, he took a pragmatic tone.

In most cases, Lipton wrote, “a corporation will be well advised to meet with the activist and discuss the activist’s criticisms and proposals, which are frequently presented in the form of a well-researched white paper. If the activist’s recommendations are not unreasonable, careful consideration should be given to adopting some or all, thereby avoiding a public dispute.”

And in some cases, he warned, “even winning a drawn out proxy battle can be more damaging to a corporation than a reasonable settlement with acceptable board representation.”

The memo could “signal a major shift in the growing battle between corporate America and increasingly hostile shareholders,” Fortune commented. “It’s a sign that the balance of power is shifting, or perhaps already has, to the hedge funds.”

Lipton, 83, has defended companies from activist investors including Bill Ackman and Carl Icahn and recently challenged Ackman to a $1 million debate on the subject. “To many in the activist world, the decision to hire Mr. Lipton’s firm … is a signal that company is willing to duke it out,” The Wall Street Journal noted.

In the memo, Lipton shared his thoughts on this week’s recommendation by proxy advisory firm Institutional Shareholder Services that billionaire investor Nelson Peltz should be voted onto DuPont’s board. Shareholders are scheduled to vote May 13 in what has been called one of the largest proxy votes in history.

“ISS and major institutional investors will be responsive to and support well-presented attacks on business strategy and operations by activist hedge funds,” Lipton wrote, and any corporation disputing an activist’s counter white paper “needs to make a compelling case.”