If the person wins, the agency can be ordered to produce the withheld documentation and to pay all legal costs. And the very filing of such a case can spotlight the campaign you are promoting. Such obvious but probing questions, if handled well, can put the government on the defensive and raise public awareness and sympathy for your case. In many situations, it is possible to use legal means to actually force government agencies and private companies to comply with various regulations. In the US, this can be accomplished through a mechanism referred to as the 'citizen suit' a provision within laws such as the Clean Water Act and the Clean Air Act which allows citizens to step in when a government agency is not doing an adequate job enforcing existing regulations.
Similar provisions are present in the laws of other countries too.
Another key component in any legal action can be the 'discovery process', which is similar in many ways to freedom of information requirements. In many countries, the legal system requires a government agency or corporation that is sued to provide the other side with internal documentation relevant to the case. The material can often provide striking support for a legal position, and it can also serve to sway political opinion, perhaps even to the point of prompting the sued entity to settle a case. For instance, in the US, documents 'discovered' during lawsuits against cigarette manufacturers revealed that nicotine levels were being manipulated to induce smokers' addiction. This revelation gave publichealth advocates the critical evidence needed to pursue stronger regulation of the tobacco industry.