But the strikers themselves say they have no intention of going back to work. As a penalty, their employer is trying to sue them for thousands of kronor each.
Striker Joakim says he knows the strike has been ruled illegal, but they still cannot accept the conditions their employer Reno Norden is trying to impose on them.
This tribunal decision only covers 29 of the workers, because the rest have doctors' notes allowing them to go on sick leave from the stress of the conflict.
In Sweden, the collective bargaining agreements that give workers their pay rises and conditions usually include a promise to not go on strike. Therefore, the garbage workers' union has not backed the latest strike and it is not protected by the laws guaranteeing freedom to strike.
The decision on Friday means that although most of the garbage collectors have handed in their resignations, the ones who are not on sick leave will have to work out their notice period.
At the moment, the company that handles the waste collection contract is having to hire new staff to keep rubbish from piling up around Stockholm.
The strike started when the staff at Reno Norden objected to a new pay deal, and to losing their control over some parts of the work process.