A United Nations expert is calling on Facebook to limit the scope of its “sweeping,” definition of terrorism over concerns it facilitates the suppression of legitimate dissenting voices.

In a letter to Facebook CEO Mark Zuckerberg, Fionnuala Ní Aoláin, an academic lawyer specializing in human rights, contended the social networking giant erroneously categorizes all non-state actors using violent means for political and social purposes as terror groups. “The use of such a sweeping definition is particularly worrying in light of a number of governments seeking to stigmatize diverse forms of dissent and opposition (whether peaceful or violent) as terrorism,” wrote Ní Aoláin.

I have consistently stressed the importance of restricting counter-terrorism measures to conduct that is truly terrorist in nature. There is a deep concern that the Facebook definition goes beyond that: https://t.co/hRjVKjZrDc — Fionnuala Ni Aolain (@NiAolainF) September 3, 2018

Ní Aoláin acknowledges that while Facebook plays an “important role,” in “offsetting terrorist activity online”, the U.N. special rapporteur says the Silicon Valley behemoth must protect the human rights of its users and allow for groups to appeal when labeled a terror group. “[I]t is unclear how Facebook determines when a person belongs to a particular group and whether the respective group or person are given the opportunity to meaningfully challenge such determination,” she wrote.

More broadly, Ní Aoláin’s warned the social network’s definition of terror could lead to “discriminatory implementation, over-censoring and arbitrary denial of access to and use of Facebook’s services.”

Ra’ad al-Hussein, the outgoing U.N. High Commissioner for Human Rights, criticized Facebook last week after the technology giant banned various high-ranking Myanmar military officials accused of “genocide” against Rohingya Muslims.

“We felt early on very uncomfortable with what we were seeing in Myanmar, (but) in the early meetings that we had with Facebook, I didn’t think they were taking it seriously,” Zeid said in a statement before reporters in Geneva. “We’ve seen from the jurisprudence of the past that if you’ve enabled, you’ve abetted, you’ve been an accessory,”

“They should be thinking proactively about what steps they will take to mitigate that,” the U.N. official added.