What's called the Basic Law - Hong Kong's "constitution" since the United Kingdom gave the territory back to China in 1997 - is clear about when Chinese military can be used in the city.
Finally, after 48 hours of civil unrest on the airport's premises, Hong Kong airport authorities were granted a judicial injunction to remove protesters from the airport on Wednesday morning according to the South China Morning Post.
The summer of conflict escalated this week as pro-democracy protesters descended on Hong Kong's airport, causing a shutdown.
Hong Kong's flagship carrier Cathay Pacific has fired two pilots over incidents connected to the city's anti-government protests.
Some of the protesters apologized Wednesday for the disruption at the airport.
A few dozen protesters remained at the airport early in the day while workers scrubbed it clean of blood and debris from overnight. Check-in counters reopened to queues of hundreds of tired travelers who had waited overnight for their flights.
"Protests at the airport can let the whole world know what is happening in Hong Kong", said Canadian tourist Jason Grafstrom. It said an area of the airport had been set aside for demonstrations, but no protests would be allowed outside the designated area.
Cathay Pacific, Hong Kong's flagship airline, has suspended a second person for misuse of company information.
She said the USA side had repeatedly denied its involvement in the on-going violent incidents in Hong Kong.
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The current president swept to power in November 2017 after long-time leader Robert Mugabe was ousted in a military coup. More than 100 MDC supporters defied that before being chased by baton-wielding officers from a city square.
President Trump on Tuesday tweeted out an alert on turmoil in Hong Kong, saying China is massing troops on the border.
In a statement Wednesday, the Chinese Cabinet's liaison office in Hong Kong said the protesters had "entirely ruptured legal and moral bottom lines" and would face swift and severe repercussions under Hong Kong's legal system.
Hong Kong protests: What is the latest?
Chinese media denied the increased presence was a reaction to the ongoing conflict but were part of planned exercises.
Last year, the USS Wasp was denied the right to visit the port in Hong Kong, as trade tensions between China and the USA ratcheted up.
While Hong Kong's crucial travel industry suffers major losses, the city's reputation as a well-regulated center for finance is also taking a hit.
But many Hong Kong residents claim the region's freedoms and democracy have been increasingly under threat.
On Aug 1, the People's Liberation Army (PLA) garrison in Hong Kong releases a slick video showing armed troops practising to quell a protest.
Some reactions on China's social media platforms called for Beijing to intervene while many others urged calm.