Labour Party (UK):

Support for the LRC was boosted by the 1901 Taff Vale Case, a dispute between strikers and a railway company that ended with the union being ordered to pay 23,000 damages for a strike. The judgement effectively made strikes illegal since employers could recoup the cost of lost business from the unions. The apparent acquiescence of the Conservative Government of Arthur Balfour to industrial and business interests (traditionally the allies of the Liberal Party in opposition to the Conservative's landed interests) intensified support for the LRC against a government that appeared to have little concern for the industrial proletariat and its problems.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What made strikes effectively legal?
unanswerable