Strikebreaking is not necessarily illegal but remember that Sweden, and EU in general, is very heavily unionized. And these unions are not insular - they someti

Strikebreaking is not necessarily illegal but remember that Sweden, and EU in general, is very heavily unionized. And these unions are not insular - they sometimes co-operate even across sector borders to defend their members' rights (and the respect for worker's rights in general). If they are so inclined, the unions have no shortage of means to force companies to co-operate. If a company is for example breaking rules / angering the unions with impunity, the trade unions can together declare an embargo on this one company. It essentially means that all union members (which in industrial sectors is close to 100% of employees) refuse to carry out orders to e.g. make deliveries or perform services for this one company. This makes it very fast completely infeasible for the company to even operate in the country as they have no access to suppliers. Because of this, companies generally know that when operating in this part of the world they can't just use strong arm tactics to suppress union activity. It's not even that hard, these unions are not run by stupid people and they are completely capable of negotiating on sensible terms.