A (relatively) recent (April 12, 2018) New York State law, Executive Law § 296-d, explicitly prohibits sexual harassment directed at non-employees.
The law provides:
It shall be an unlawful discriminatory practice for an employer to permit sexual harassment of non-employees in its workplace. An employer may be held liable to a non-employee who is a contractor, subcontractor, vendor, consultant or other person providing services pursuant to a contract in the workplace or who is an employee of such contractor, subcontractor, vendor, consultant or other person providing services pursuant to a contract in the workplace, with respect to sexual harassment, when the employer, its agents or supervisors knew or should have known that such non-employee was subjected to sexual harassment in the employer’s workplace, and the employer failed to take immediate and appropriate corrective action. In reviewing such cases involving non-employees, the extent of the employer’s control and any other legal responsibility which the employer may have with respect to the conduct of the harasser shall be considered.
This law demonstrates New York’s commitment to ensuring that its workplaces are free of sexual harassment in its many forms.