Most climate change litigation is at least partially based on fundamental rights.

Those may be rights derived from the national constitution (or even from a sub-state constitution) or a national bill o rights. For example, the German Klimaklage (Neubauer, et al. v. Germany) was mainly based on fundamental rights and freedoms protected by the German constitution, such as the right to life and physical integrity, protection of property and human dignity. The Canadian La Rose case is also partially based on rights under the Canadian Charter of Rights and Freedoms.

Other claims are based on international human rights norms, for example those of the European Convention on Human Rights, the Inter-American Convention on Human Rights, or the International Convention on the Rights of the Child.

This is the case, on the one hand, where litigants bring a claim directly with international tribunals such as the European Court of Human Rights. On the other hand, litigants may bring claims in national courts and base them on international human rights norms if their jurisdiction does not have its own code of human rights (such as the United Kingdom), or if the national code of human rights is less extensive than international human rights norms. Yet another possibility is that the national jurisdiction has a code of human rights, but the national courts do not have the competency to adjudicate violations of these fundamental rights. The latter was  the case in the Dutch Urgenda case. While the Netherlands have a code of human rights, Dutch courts do not have the competency to review whether acts of Parliament comply with it, and thus declare such acts of Parliament invalid. However, courts may declare legislation invalid if it violates international law. For this reason, the litigants in Urgenda based their claim on norms of the European Convention of Human Rights, rather than on Dutch human rights norms.