In 1997 during the handover ceremony for Hong Kong there was a part that involved the PLA marching into Hong Kong.
https://www.youtube.com/watch?v=G4-Sr_t_kE4
To pretend that they weren't in control of the situation when he was there from a national security standpoint is a bit naive. Ultimately the decision to allow him to depart Hong Kong was made in Beijing.
https://www.nytimes.com/2013/06/24/world/asia/china-said-to-...
"The Chinese government made the final decision to allow Edward J. Snowden, the former National Security Agency contractor, to leave Hong Kong on Sunday, a move that Beijing believed resolved a tough diplomatic problem even as it reaped a publicity windfall from Mr. Snowden’s disclosures, according to people familiar with the situation."