The National Labor Relations Board’s approval of an employer no-camera rule is just the beginning of anticipated handbook rule changes for employers under the now Republican-dominated agency, experts predict.

In June, NLRB General Counsel Peter B. Robb issued a memo that provides new guidance on employer handbook policies and states that ambiguities should no longer be interpreted against the employer.

The 20-page memo covers rules including insubordination, confidential information, defamation, use of the employer logo, authorization to speak for the company and rules banning disloyalty.

The memo referred to the board’s December ruling that overturned a 2004 decision and held that Chicago-based Boeing Co. had lawfully maintained a no-camera rule in its employee handbook.

The Boeing rule prohibited employees from using camera-enabled devices to capture images or video without a valid business need and an approved camera permit.

Citing the Boeing rule, the NLRB said in a June 14 advice memo that two workplace rules, one prohibiting use of logos without express written approval, and another prohibiting use of proprietary and confidential information that includes “user information,” were not overly broad.

The memo was written by Jayme L. Sophir, associate general counsel, division of advice, to San Francisco-based NLRB Regional Director Jill H. Coffman, and concerned San Francisco-based Lyft Inc., the ride-sharing service. The rules are in Lyft’s terms of service agreement.

The Robb guidance is welcome to employers, say experts.

It “clarifies that some common types of handbook policies, such as policies that require collegiality, cooperation, teamwork and policies that prohibit common types of problematic conduct remain lawful, notwithstanding some decisions from the prior NLRB” while still permitting employers to prohibit insubordination, certain types of disparaging statements and other conduct that can undermine an employer’s interests, said William J. Kishman, of counsel representing employers in matters involving employees and labor unions with Squire Patton Boggs in Cleveland.

The guidance removes the possibility of employers being charged with unfair labor practice violations for normal workplace rules and policies, said Michael Starr, a partner in the labor and employment practice of Holland & Knight L.L.P. in New York. “I think the major implication of this is that it restores the law to where it really had been about 15 or so years ago, before the labor board tried to regulate more intensely in this area,” he said.

William H. Floyd III, a partner and labor and employment law specialist with Nexsen Pruet L.L.C. in Columbia, South Carolina, said: “Under the prior administration’s interpretation, there was a lot of discretion and uncertainty as to which policies should be enforced, and what their content should be.”

The new administration’s policy “makes it more balanced evenly, weighing the employer’s need to communicate information, and the employee’s rights” under the National Labor Relations Act.

The guidance “means that more handbook rules are going to be found to be lawful,” said Barry J. Kearney, of counsel with Cozen O’Connor P.C. in Washington and former head of the NLRB’s advice division.

By providing examples of the kinds of rules that will be permitted, Mr. Robb’s memo guides employers who are drafting new rules or updating old ones “as to how likely the general counsel would view them to be lawful or unlawful,” he said.

“There’s more of a balance in the way they’re trying to view things, so it’s not necessarily so pro-worker, and there is some recognition there” of business interests, said Fiona W. Ong, an employer defense attorney and partner with Shawe Rosenthal L.L.P. in Baltimore.

In the Boeing case, for instance, the approach now is not whether the rule could affect or chill worker rights, but whether it is likely to do so. “It brings back an element of common sense to the rule to what it was intended to do, rather than the most extreme position someone could take on the rule,” Ms. Ong said.

Labor and employment law attorney Dabney D. Ware, of counsel at Foley & Lardner L.L.P. in Jacksonville, Florida, said the prior rulings “were so convoluted that it created a lot of opportunity for companies to be held liable for something where they were really just asking everyone to play nice together.”

Meanwhile, experts say one case ripe for reconsideration is Purple Communications Inc. and Communications Workers of America, AFL–CIO, which allowed workers to use employer email systems for union business. It requires employers to make their corporate email systems available for group discussion among employees about the terms and conditions of their employment during nonwork time, including for union organizing.

The 2014 ruling overturned a 2007 decision that said employees did not have a right under the NLRA to use employer-owned email for organizing purposes. Purple Communications “was a real game changer” that “caught employers a little flat-footed,” said Ms. Ong.

Mr. Robb did not mention the ruling in his most recent guidance but cited it in a December memo asking regional officers to submit cases involving significant legal issues, including those that overruled precedent and involved one or more dissents.

Purple Communications is “really the next shoe to drop,” said Steven M. Bernstein, a partner and labor attorney with Fisher & Phillips L.L.P. in Tampa, Florida.