Criminal law has been widely used around the world to protect nature, but how to structure it for optimal protection remains unclear. This Article proposes a framework for applying criminal liability to offenders who create a risk of harm or harm to nature. First, it offers three models for liability, including abstract endangering, actual endangering, and independent/autonomous crime. Second, criminal penalties applied should be effective, dissuasive, and proportionate, including fines and imprisonment as well as remedies that restore the original state of nature and prevent future damage. Third, when corporations commit crimes against natural resources, both the corporations and individuals involved should be subject to criminal liability. The Article finds features of the framework within international and regional instruments, such as (1) the Convention on International Trade in Endangered Species of Wild Fauna and Flora, (2) the Rome Statute, (3) the Conventions on the Protection of the Environment Through Criminal Law, and (4) the Environmental Crime Directives. However, several problems can impede enforcement of criminal nature conservation laws, including (1) limited capacity and knowledge of judicial authorities; (2) lack of deterrence/dissuasion of potential offenders; (3) poor enforcement at the national level; and (4) lack of international cooperation.