Politicians taking office in Hong Kong's Legislative Council (LegCo) must swear allegiance to the city as part of China, the mainland's parliament declared on Monday—a ruling likely to further inflame the territory's tense political atmosphere and aggravate anti-Beijing sentiment.
"Certainly, we can expect more protests to come," said Linda Li, a professor at City University of Hong Kong, told CNBC.
Ahead of the news, as many as 11,000 demonstrators took to Hong Kong streets on Sunday to protest Beijing's involvement in a legal matter concerning two LegCo lawmakers who insulted China during their swearing-in ceremony. Chaos rapidly ensued, with people using umbrellas as protection from police pepper spray in scenes reminiscent of the city's 2014 pro-democracy Umbrella Movement.
David Wong, deputy at the National People's Congress (NPC), which is effectively China's parliament, also expected more demonstrations.
"We can anticipate strong reaction. A small minority of Hong Kong's population remain adamant on this issue so I wouldn't be surprised if they took to the streets again," he told CNBC's "Squawk Box."
On October 12, Sixtus Leung Chung-hang, 30, and Yau Wai-ching, 25, pledged allegiance to "the Hong Kong nation" and held a banner saying "Hong Kong is not China" during their oaths, ignoring the original wording. In retaliation, the city's Beijing-backed Chief Executive C.Y. Leung requested the courts oust the duo from LegCo, and a judicial review began on Thursday to decide whether the pair can retake the oaths.
But the mainland also began a meeting on Thursday to discuss their matter and its decision on Monday, which banned Leung and Yao from office, will now override the local court. CY Leung said on Monday that his government would "fully implement" China's interpretation of the Basic Law, which sets out China's policies related to Hong Kong.
The interpretation, Beijing's most significant form of legal intervention since Hong Kong's sovereignty was transferred from the U.K. to China in 1997, would defend national unity and sovereignty, deputy secretary general of the NPC Standing Committee Li Fei said in a Monday press conference.
The NPC's Wong defended China's actions, saying he did not see the interpretation as Beijing pre-empting the Hong Kong courts.
"When we talk about Hong Kong independence, that's not a local issue, it's a national issue concerning territorial integrity so Beijing has a natural role in all of this," he argued. "To do this interpretation, its within the confines of Basic Law as well."
A total of five lawmakers had their original oaths invalidated last month but three of them have since retaken their pledges and were officially sworn-in, and are expected to be exempt from Monday's decision. Top mainland official Zhang Xiaoming said on Sunday that "it could be complicated to disqualify lawmakers who had finished their oaths," according to the South China Morning Post.
Yau Wai-ching and Baggio Leung will now be forced from office and by-elections will be called, Chong Ja Ian, assistant professor at National University of Singapore, explained.
"More direct Chinese involvement into Hong Kong has been a trend; this is likely to increase tensions as many find this kind of Chinese role in Hong Kong hard to accept," he said.
The big question on everyone's mind was whether Monday's decision would set a precedent for more Chinese interference in the SAR's legal system.
Li Fei said on Monday that Beijing policymakers would "only interpret the Basic Law on important issues, but not on Hong Kong's internal affairs". He also noted that that the central government would not be "obscure or lenient" in quashing acts that promoted Hong Kong independence.
However, that all depended on the actions of Hong Kongers, experts said.
"It really depends whether the city's situation continues to deteriorate. If it does, the central government will see that it has no other means except to intervene. But that's the worst-case scenario, Beijing doesn't want to do that as its not in China's best interest to let the situation worsen,' explained professor Li.