The private attorney general doctrine is critical for protecting private citizens and institutions from government intrusion and bullying. In a nutshell, it requires the government to pay a prevailing public-interest plaintiff’s costs and attorney fees. Why? Because it would otherwise be impractical for wronged parties to pursue such lawsuits.
For example, an individual whose Freedom of Information Act request is unlawfully rejected would be entitled to a court order requiring the government to comply, but that piece of information likely would not be worth the court costs and attorney fees necessary for such an order. Therefore, if the plaintiff prevails and the government is required to produce the requested documents, then the court will also order the government to pay his costs and attorney fees.
In other words, monetary resources are not insurmountable obstacles to a plaintiff who wants to defend a public right. This can range from opposing infringements of free speech and religious freedom, to forcing government compliance with information requests, among other examples.