Asks a friend of a friend on Facebook:

Not absolute sure if legal legitimacy is close to moral legitimacy... Can contravention of the law be justified on moral grounds?

Legality and morality are not the same.

From [Bastiat's The Law] :

"The law perverted! And the police powers of the state perverted along with it! The law, I say, not only
turned from its proper purpose but made to follow an entirely contrary purpose! The law become the
weapon of every kind of greed! Instead of checking crime, the law itself guilty of the evils it is
supposed to punish!"

And then:

"When law and morality contradict each other, the citizen has the cruel alternative of either losing his
moral sense or losing his respect for the law. These two evils are of equal consequence, and it would be
difficult for a person to choose between them."

What we are seeing in Hong Kong is the breakdown in respect for the law because it is being abused and used as a tool to achieve what a large portion of HK society feels is an immoral ends.

You can see this to a larger extreme in mainland China. The Party writes the law so the law says whatever is convenient to the Party; people see little legitimacy in the way the laws and therefore either ignore laws or follow them solely out of fear of punishment not out of a respect.

Society works best when people accept laws as the rules to the game - it is costly (and not very effective) to use force to compel large numbers of people to accept a system they find unjust no matter how "legal" that system is.