Following the heightened violence at Polytechnic University in Hong Kong over the weekend, U.S. Senator Josh Hawley (R-Mo.) today suggested that China may be in violation of the 1984 Sino–British Joint Declaration. According to BBC, “around 100 people tried to leave the Polytechnic University, but were met with tear gas and rubber bullets.” The Washington Post reported that Chinese President Xi Xingping recently urged Hong Kong authorities to take “firmer action” to end the protests.

“#HongKong police trapping hundreds of students inside #PolyUniversity. Won’t let them leave. Apparently want mass arrests. These actions by Beijing-backed govt raise question whether #China is in violation of its 1984 Joint Declaration commitments,” Senator Hawley said on Twitter. “The 1984 Joint Declaration, a duly ratified international treaty, controls the status of #HongKong, not the whim of Beijing.”

The Sino-British Joint Declaration, which was signed in 1984 by then British Prime Minister Margaret Thatcher and Chinese Premier Zhao Ziyang, guaranteed Hong Kong’s rights and freedoms under the “one country, two systems” formula.

Senator Hawley introduced the Hong Kong Be Water Act and is an original co-sponsor of the Hong Kong Human Rights and Democracy Act. Both pieces of legislation aim to hold Beijing accountable for its actions in Hong Kong.