Ethics watchdogs who have long warned of the potential conflicts posed by the Trump family’s business interests were quick to cry foul on Wednesday. Importantly, they also saw it as a potential new opening to take Trump to court.

Currently, the most high-profile legal challenge to Donald Trump’s business empire concerns what is known as the Emoluments Clause in the U.S. Constitution, which bars U.S. officials from accepting payments from foreign governments. While many ethics experts agree that Trump is violating that law by accepting money from foreign diplomats who stay at his hotels and from state-run companies that lease office space in buildings he owns, the lawsuit ultimately faces a separate challenge: the question of standing.

In order to sue someone, plaintiffs generally need to prove that they were specifically harmed by the alleged wrongdoing in question. It is unclear, however, if the group behind the emoluments suit—the ethics watchdog Citizens for Responsibility and Ethics in Washington, or CREW—will be able to check that box. The organization claims that since its mission is to investigate corruption, Trump’s actions represent a drain on resources that would otherwise be spent investigating the group’s usual areas of interest, such as campaign finance. There’s some precedent to support such a claim but not a lot, and courts tend to be skeptical of such broad assertions of standing outside of the context of civil rights violations.

Trump’s Nordstrom tweet might be a different story, though. Norm Eisen, who served as the chief ethics lawyer for the Obama White House and who is working with CREW, suggested on Twitter that Trump’s comments gave Nordstrom standing to sue him under unfair competition laws, particularly California’s state law, which protects against any business practice deemed “unfair,” “unlawful” or “fraudulent.” While the president is generally shielded from lawsuits over his official conduct while in office, that blanket protection does not apply to his private or business conduct. Nordstrom, however, would need to be able to show it was harmed economically. More immediately, though, the company would have to decide if it’s worth the risk of further angering a president who has yet again made it clear that he’s willing to single out specific companies that dare cross him.