Isn't that cartel-like behavior and basically extortion? How is that legal?

There is a concept called Solidarity, which Swedes take very seriously. If one employer chooses to not play fair by the rules of the labor market (which include negotiating with unions in Sweden) then other unions will show Solidarity with the one striking. The unions act with the mandate from the workers. They are not dictatorships.

Historically solidarity between workers is the reason why you only work 8 (instead of 16) hour days. Why workers have vacation days, sick pay, pensions and maternity leave etc.

https://en.wikipedia.org/wiki/Solidarity

If labour cartels are allowed in Sweden, why aren't pricing or other cartels allowed?

On the labour market they are allowed. Unions typically negotiate with employer’s organizations with most businesses as members. Also, labour conflicts are adjudicated in a special court made up by representatives from unions and employer organisations. Kind of like arbitration, but it’s sanctioned by law.

Why? We don’t trust the state to do it better. Neither employees nor employers do.

Did you mistake my comment with another? I was asking why other types of cartels are treated differently.

Short answer is that all parties involved (the State, the Employers and the Employees) want this particular type of cartel to be treated differently from other cartels. The government could change that at any time by passing a law, but they don't because it would be wildly unpopular with everybody.

Ah, i may have misread. I thought you asked why only the employee side were allowed cartels, which is not the case.

By your..."reasoning" voting with your wallet is extortion

"Other people are using their own free will and self determination to undermine a CORPORATION!"

If there's one cartel that should get a pass surely it should be a country-wide labor cartel, right?

Its a free market for labor.

If they aren't operating in explicit coordination, no.

Cartel behavior requires coordination and collusion. If they are just following general social/business practices without having meetings about who to blacklist, then it doesn't meet most definitions.

I upvoted you because you’re technically right. It’s permitted because it generally leads to good social outcomes at the expense of business profit. This isn’t cost-free, of course. Nothing is. It’s just that Sweden believes the costs are worth it. By the numbers, outcomes for citizens are very good, so I think they’re correct.

This is another difference from the US. Certain forms of solidarity action are illegal in the US.

The TL;DR of US labor law is:

1. Companies do [very illegal under local law, up to and including murder] things to bust unions; they buy off the local authorities to get away with this.

2. The Federal government adds specific protections for unions -- many of which don't exist in various European countries.

3. Companies complain that #2 makes unions too powerful, so the Federal government adds specific restrictions on unions -- many of which don't exist in various European countries.

I'm curious about the history in Europe, since an equilibrium seems to have been found without steps #2 and #3.

I don’t know about Europe at a whole, but there are examples of unions also employing step 1). Like, announce a strike and then beat up or even murder people working anyway.

Also many unions did what business owners had done for centuries and went into politics. The social Democratic party in Sweden for example, is a part of the largest labour union. This is somewhat controversial in some circles, for sure, but changes the power dynamic for steps 2 and 3 a lot.