In the wake of for helping shareholders get their corporate board nominees on the ballot, law firms are telling companies not to be complacent.

A second rule, unaffected by the court's decision, still encourages efforts by activist shareholders to seat directors --- even if the procedure that investors must adopt is slightly more complex. And that demands awareness on the corporate front.

"Investor relations departments should be aware that proxy access may be a potential issue for certain shareholders," , "and may want to prepare general talking points on this topic to use should questions arise when talking to investors."

It adds that other proactive measures also could be in order: "Some public companies might consider it prudent to adopt and incorporate into their bylaws a proxy access mechanism that is more company-friendly than one that shareholders might propose...," its memo says. Such a move could "preserve a possible argument that any subsequent proxy access shareholder proposal has been 'substantially implemented' and is thus excludable," it writes, under the existing rule that wasn't overturned by the court.

Suggesting that there could well be more battles ahead, Mayer Brown adds that "there is no guaranty that the SEC would accept such an argument, especially if the management proposal were narrower in scope" than what investors seek.