This is an excellent point I've struggled to put across. Furthermore people act like laws are set in stone and are always objectively Good. "It is illegal" is in some cases not a good argument against something.

Laws are usually there for a reason.

You could apply your whole argument to public opinion and referendums - public will change mind a lot, why make such drastic moves based on it?

Usually laws are there for a reason. Then sometimes we have to repeal "slavery is OK" or "black people count for 3/5 of white people" or "women can't vote" laws. Because they're obviously wrong.

There never was a black people count for 3/5 of white people.

It was “states that have slavery get to count 3/5 of their enslaved population when determining the representation the free population gets in Congress (and, hence, also it's voting power in Presidential elections.)”

It's actually worse than black people counting as 3/5 of a white person; its more like slaveholders counting as 1 + (slaves held × 3) / 5 people.

Thanks for clarifying - my knowledge of US history is bad. But the point stands - bad laws exist and "it is the law" does not necessarily mean "it is right"

Ok that's a good point. I guess I am too spoiled by modern mostly-making-sense laws and annoyed by the neverending "government is bad" rants.

On the other hand, public supported all those "bad" laws at the time ... But yeah, I was wrong, illegality on its own is wrong argument.

Plenty. India, Kenya, Australia, Canada and various ex-SSRs all spring to mind. Not many without violence on the run-up, I'll grant you, but in many cases, the actual process of independence was performed entirely legally.

Saying that India got her independence legally is quite a stretch. There were plenty of mutinies, bloodshed, violent and non-violent movements before the British (massively weakened by the WWII) decided that they had enough. While it is true that India did not declare unilaterally declare independence (some leaders did, but they did not gain widespread public support) and start a civil war, the independence movement itself was not legal and most leaders were branded terrorists and incarcerated.

Yes, often quite a bit of violence in the run up. Whether the imperialist side wants to try and look good at the point of capitulation or not has little to do with how “legal” the effectual parts of fighting for independence are.

To suggest that, e.g. Gandhi didn’t have a meaningful role in achieving India’s independence, because the British considered his actions illegal, is very silly.

ex-SSRs can be a good example but ex colonies isn't a fair comparison with Catalonia

I'm from ex-Soviet country called Lithuania, and no, although Lithuania was the first country to declare independence from the Soviet Union, it was not done within Soviet legal framework in any way.

From my own short experience, FYROM from Yugoslavia and Montenegro from Serbia.