In 2010, retaliation became the most frequent type of charge received by the Equal Employment Opportunity Commission (the “EEOC”). In the wake of the United States Supreme Court’s ruling in Thompson v. North American Stainless, LP, 131 S. Ct. 863 (2011), that trend is likely to continue, particularly due to the fact that the Court refrained from answering the most difficult question implicated in third-party retaliation claims.

The Court in Thompson unremarkably decided that (a) Title VII prevents an employer from retaliating against an employee due to the employee’s association with an individual who participated in protected activity (“complaining employee”); and (b) the third-party employee has a cause of action for retaliation under Title VII, despite the fact that the individual did not actually participate in the protected activity. These determinations were hardly ground-breaking; indeed, the EEOC Compliance Manual asserted the same principles.

But the most difficult question of all — “what type of relationship gives rise to prohibited third-party retaliation?” — was barely addressed by the Court. Justice Scalia described the Court’s conclusions in this case as “obvious” because Thompson was the fiancé of a complaining employee, and he alleged that he was terminated due to this relationship. The Court specifically stated that it would not “identify a fixed class of relationships for which third-party reprisals are unlawful.” Justice Scalia nonetheless opined that terminating a close family member will almost always meet the standard, while a mild action against an acquaintance “will almost never do so.” As a result, in analyzing future cases, courts will evaluate the nature of the third-party’s relationship with the complaining employee and the severity of the employer’s action.

This ruling provides yet another reason that employers should have well-documented, consistent, and well-reasoned grounds for taking disciplinary action against employees, especially employees in relationships with complaining employees. When a complaining employee has a co-worker that is a sibling, close friend, or significant other, some employers worry that the third-party employee will act as a mole in the complaining employee’s discrimination case. Rather than terminate the third-party employee, employers should closely guard information that they want to keep confidential.

While we wait for the district courts to begin laying out the standards necessary to assert a prima facie case for third-party retaliation, employers should carefully consider actions taken against a third-party employee when they know that the employee has a relationship with a complaining employee.