Recognising Rights of Nature
One of the most progressive constitutions in existence to date is the most recent Constitution of the Republic of Ecuador (2008), (Spanish version, English version), which included Rights of Nature in Articles 71-74.
Recognising Right to Environment
Though arguably not Earth Law, but starting to move in a positive direction by recognising rights and duties in relation to the environment, many countries take a more anthropocentric approach in their constitutions, by recognising the right to environment of individuals, groups and communities. See Annex 2 of the International Commission of Jurists (Dutch Section) 2011 Report on Human Rights and the Environment for a list of constitutions that contain provisions on rights and duties in relation to environment.