In this article we conduct a research into a highly controversial subject. We mean the constitutional control of laws in its 2 basic forms: the previous control and the posterior control. We conclude that previous control is an abstract one and enjoys certain advantages: - Removes the constitutional conflict until the entry into force of the law; - Reduce the period of notice and consideration; - Is a formula that puts in a certain relationship parliamentary sovereignty and judicial review and absolutely does not violate the prestige of the legislature; - Contribute to the legislative stability and removes negative consequences that may result from posterior control in cases where laws have been declared unconstitutional. By posterior control of the constitutionality we distinguish the constitutionality of laws and other normative acts after their entry into force. Posterior control exists in the states where the constitutionality of laws is exercised by the courts of common law and in the states in which control is exercised by the constitutional courts (tribunals).