Final answer:
In international law, laws are applicable only to those states that voluntarily agree to be bound by them through treaties and adherence to customary practices. Enforcement is complicated due to a lack of global executive power, making compliance reliant on state willingness and collective international pressure.
Step-by-step explanation:
The statement that in international law, laws are applicable only to parties who voluntarily choose to participate in them is true. International law consists of a complex mix of treaties, conventions, and customary legal practices that govern state behavior on a global scale. Sovereign states agree to be bound by these laws through the ratification of treaties and demonstrate adherence to customs over time, which become recognized as binding. While the UN serves as a repository for these international treaties and promotes adherence, the enforcement of international law is challenging, due to the absence of a global executive authority.
There are situations where powerful states or alliances may enforce laws, adding a political dimension to compliance. Moreover, treaties like the Paris Climate Accord or the Universal Declaration of Human Rights require states to modify their domestic policies to align with international commitments, hence extending the reach of these international agreements into domestic spheres. However, since there is no central authority to enforce these laws, their effectiveness relies on the willingness of states to comply and the collective pressure from the international community.