Harassment by Non-employees is exactly what it sounds like. 

Employees, who are harassed by customers, vendors, temp workers, outside contractors, tec. still retain their rights to a harassment-free workplace. 

As an employer, you cannot disregard the situation.  The courts have upheld your responsibility in this area.

Remember: an employer must investigate and respond appropriately to the allegation even if it appears trivial or contrived. 

It is also in the employer's best interest to take some action whether the claim has substance or not.  Document the incident, require additional training, etc.

Non-Employee Sexual Harassment
In California, a plaintiff filed a non-employee sexual harassment claim because her employer, International Business Machines Corp. (IBM), pressured her to resume a sexual relationship with a Defense Department official who had the authority to award IBM millions of dollars in project funding.

Award: $65,000 in monetary damages