The best way to prevent employees from rallying support for a union in the workplace is to write and enforce a specific no-solicitation policy. To make sure it passes legal muster, your policy should:
1. Prohibit solicitation during work time.
2. Ban distribution of literature or other materials at all times in all work sites.
3. Prohibit nonemployees from soliciting at any time on your company property.
Then, post the policy in a prominent place, include it in your handbook and require employees to sign it as acknowledgment.
As the following case shows, simply publishing a vague policy won't save you. To discourage solicitation of your employees, you must make sure everyone is aware of your rule and be willing to enforce it. This can mean strict interpretation.
Example: if you want to stop employees from handing out fliers on the shop floor that promote a union meeting, you also have to crack down on employees who want to distribute pamphlets for an upcoming Girl Scout cookie sale.
Recent case: After a company won a union election, the union appealed under the National Labor Relations Act, claiming the company's no-solicitation policy was too broad.
The National Labor Relations Board (NLRB) agreed that the policy, which stated that "vending, soliciting or collecting contributions for any purpose is prohibited unless authorized by", could be seen as overly vague. But it still upheld the election results, saying the policy wasn't enacted in response to the union campaign.
But in a warning to other employers, the NLRB said that vague or overly broad handbook language may, in other cases, be sufficient to overturn elections won by the employer. (Delta Brands, Inc., 344 NLRB No. 10, 2005)