I'm not sure how familiar you are with employment laws in Sweden, but you cannot just fire people willy-nilly, you need to have "Objective grounds for dismissal" in order to fire someone. For example, you are not allowed to fire someone because they're participating in a union, as a employer you'd be setting up yourself to get sued if you do this.

Question is, what "participating" actually refers to. One could make the case that striking is just a part of normal participation in the union, while one could also make the opposite case of course. In the end, seems it'd be up to the courts to decide.

There is a right to strike in the Swedish law as well. As long as the strike is legal (has to be a union involved and follow certain procedures) the employer definitely can not fire anyone. And the union in a case like this is paying all the employees 100% of their salaries while it is ongoing, for however long it will take.

In Sweden, the union can blockade a company that they are "negotiating" with.

That means that all other unions will refuse to work with that company, and this goes for both suppliers and customers of the blockaded company. No more transportation services, buying parts, getting service people to show up when your equipment is broken, delivering your goods to customers, etc.

So, being blockaded is a risk which should be known going in.