After 9/11 a number of governments committed their armed forces to military operations abroad and introduced far-reaching emergency restrictions of individual rights without substantial parliamentary scrutiny. In many cases, the executive branch argued that it needed considerable leeway to counter terrorist threats, and most legislatures followed suit. The article looks at the operational difficulties of parliamentary involvement from a comparative perspective, focusing on the legal situation in Germany, the United States and the Russian Federation. It identifies the purpose of parliamentary review and demonstrates that the principle of the separation of powers shall not be renounced in times of global threats or replaced by the fusion or shift of powers. On the contrary, the separation of powers as the basis of a modern constitutional democracy strengthens democratic control and enhances individual liberties, while not putting into question the executive's flexibility. The legislatures' participation in the most important decisions leads to a stable and sustainable use of executive power. However, the division of competences must observe the respective strengths and weaknesses of the branches of government. Thus, it is not the function of Parliament to regulate the operational details of military operations.