Street demonstrations in Hong Kong on Sunday ended in a cloud of pepper spray, as Beijing conducted its most dramatic intervention in the semi-autonomous territory’s politics since 1997.

Reuters describes Sunday’s protests as “reminiscent of pro-democracy protests in late 2014 that paralyzed parts of the Asian financial center and posed one of the greatest political challenges to the central government in Beijing in decades.”

A leader of those earlier demonstrations, student activist Joshua Wong, declared that China’s Basic Law is a “handicapped legal document, and the so-called mini-constitution can be amended and controlled by the Chinese Communist Party at will.”

Wong referred to a new requirement imposed by the National People’s Congress in Beijing that Hong Kong’s elected officials must swear allegiance to Hong Kong as a part of China. The new rule disqualifies candidates who modify the oath of office, or even “fail to take it in a sincere and solemn manner.”

Protesters saw this ruling as an effort to block two specific young politicians from taking office. 25-year-old Yau Wai-ching and 30-year-old Baggio Leung were notably short on sincere and solemn obedience to Beijing when they unfurled a banner declaring, “Hong Kong is Not China” during their swearing-in ceremony last month.

They also deliberately misread their oaths of office to leave out the parts Beijing really likes. For good measure, Leung used a derogatory Japanese slang term for China in his oath, while Yau “slipped what sounded like a profanity into the phrase ‘People’s Republic of China’ when she recited her oath,” according to the New York Times.

The Wall Street Journal reports that the National People’s Congress of China denounced the actions of the Hong Kong lawmakers as a threat to national security, and said it “cannot afford to sit idle” in the face of such a challenge to Beijing’s authority.

Hong Kong courts are conducting a judicial review to decide if the two upstart politicians should be permanently disqualified from office, but Beijing evidently decided not to take any chances on local judges coming up with the “wrong” answers.

“Hong Kong’s legal community has said that Beijing stepping in before the judicial review ruling is a serious blow to the city’s rule of law and to its semi-autonomous status,” AFP reports. “The pro-democracy camp has also accused the Hong Kong executive and Beijing of riding roughshod over the legislature to stop democratically elected representatives taking up their positions.”

The Wall Street Journal spotted some familiar faces from the 2014’s “Umbrella Movement” on the streets of Hong Kong Sunday night. They seemed a bit shocked that Beijing would provoke a crisis with such heavy-handed intervention in their election. Some called for greater autonomy, while others said they merely wanted China to respect the agreement already in place.

“The police was using very brutal violence to depress us. We were very angry because we think that for such an important issue, we at least have our right to protest,” said 25-year-old Nathan Law Kwun-chung, also the winner of a recent election.

“We don’t know what’s the next move. We are just trying to occupy,” said 25-year-old Hang Tsoi.

Protest leaders called off the demonstration at roughly 1:00 AM local time, worried about further confrontations with the police. A “silent march” by lawyers is planned for Tuesday.

According to AFP, the legislature has been effectively “hamstrung” by the battle over Yau and Baggio, with parliamentary sessions dissolving into chaos violent enough to injure six security guards to date.

Beijing has only stepped in to interpret the Basic Law six times since the handover of Hong Kong in 1997, and on all six of those occasions, Hong Kong asked for the ruling.