This is seemingly the most logical question any pro-establishment politician or member of the pro-government camp would put to the untamed anti-everything-China yellow camp. True, the US and other western countries all have their national security laws. So, why are you applying a different standard to your own country?
But if you put the implementation of national security in the Chinese context, applying a double standard could be fully legitimate and even necessary. Track records of law enforcement in China have already proven how violation of national security laws can be a wild-card allegation for anyone who challenges the central leadership, and how far the way trials are conducted in a Chinese court is from the civilized world, not to mention the candid trials and deprivation of rights to properly defend against the allegation. The independence of the judicial system is not even questionable; it simply does not exist in China as the judicial system is supposed to serve and collaborate with the government. It is not difficult to understand the rationale behind choosing specific judges by the chief executive to handle cases brought by the new security legislation and how unimportant the perception of conflict of interest is for China. (Some people would have deliberately confused the titular role of the chief executive in appointing judges with choosing judges for trials.) Ignoring these fundamental differences, one has no basis on which to discuss whether the same standard is applicable to assess even the reasonableness of establishing and implementing the same Chinese national security law in Hong Kong.
When a US citizen criticizes the government, chants anti-government slogans, or demands the president to step down, he does not violate any national security law. But when a Chinese citizen does the same, he can be prosecuted for "endangering national security" or "inciting subversion of state power", and the conviction rate is 99%. The root difference is that an American can vote the government out, but a Chinese must accept the government or he will face prosecution. Environmentalist Tan Zuoren, who advocated an inquiry into the substandard school buildings causing deaths of hundreds of students during the 2008 Sichuan earthquake, was sentenced to 5 years in prison for "inciting subversion of state power". Food safety worker Zhao Lianhai, who was also the father of one of the many victims of the melamine-tainted milk products, was sentenced to 2½ years imprisonment for "disturbing social order". Human rights lawyer Huang Quanzhang was held incommunicado (virtually disappeared) for three years since August 2015 and was put on trial for the wild-card allegation of "subversion of state power" in August 2018, and released in April 2020. The case of Nobel Peace Prize winner Liu Xiaobo needs no elaboration, he was convicted for making a political reform proposal. None of these cases, from arrest, trial to conviction, was compliant with western standards.
Double standard or not? It's up to you to judge!
June 24, 2020
________________ PS: All discussions now will remain purely academic, as the new national security laws will be implemented anyway, and the only hope we have is the reduced level of arbitrariness and better transparency under the common law system if trials were still allowed to be conducted in a Hong Kong court.