Balfour Beatty failed to obtain an injunction against the Unite union at the High Court last Thursday.
They wanted the strike ballot to be deemed unlawful.
Balfour electricians voted by two to one for a strike for the second time earlier this month.
This time the union defended itself against the threat of an injunction.
The company argued the strike vote process was flawed.
But Judge David Eady disagreed. He said, “It seems clear that any such failures would be unintentional,” and that “balance should be struck between striving for democratic legitimacy and imposing unrealistic burdens on unions and their officers”.
Bosses argued that under section 230 (2) of the Trade Union and Labour Relations Consolidation Act, Unite had failed to ensure everyone who was entitled to a vote received a ballot paper.
However, in his judgement, Justice Eady said, “It is clear that parliament intended that the practical realities should be taken into account and, in particular, the difficulties from a trade union’s point of view of maintaining records of members which are completely accurate and up to date.
“There are particular difficulties in identifying Unite members employed by BBES.
“The construction sector is an industry in which workers regularly move on from site to site and also change employers.”
In recent years judges were often willing to grant injunctions to stop strikes whenever bosses challenged unions.
Strikes at Metrobus, EDF, Milford Haven and Network Rail, were all stopped in this way.
This latest decision shows it’s always right to fight any threat of an injunction because it is legally possible to have an official strike—just.