Thus it had certain reduction of the power to contract, for a bigger interest, a collective and solidary interest. If it does not treat to breach the directive power that the citizens have in relation its lives, but the dosage of these primates when the exercise of a private law and egostico comes to injure diffuse interests. The general objective of to be made study is to verify the obligatoriness of pacta ahead sunt servanda of the social function of the contract and the free private initiative. E, of form to reach this goal, to confirm or not it declared hypothesis previously, has that to mark itself, especificadamente the following stages: to verify by means of bibliographical research, historically and currently the advantages and disadvantages in such a way of the social function of the contract how much of the free private initiative, to observe the difficulties found in the applicability of article 421 of the Civil Code in the Brazilian society, according to which the freedom to contract will be exerted in reason and the limits of the social function of the contract and to approach to this new ditame with the Code of Defense of the Consumer. 2. The Federal Constitution of 1988 and the Civil Code of 2002, principles and social function The Federal Constitution of 1988 brought as fundamental principle the protection to the rights and individual guarantees of the man (art. 5), treating more specifically to the one to the Dignity to the Person Human being in its articles (article 1 interpolated proposition III), influencing all the Brazilian legal system. One of the also determinative reasons in this Constitution is interpolated propositions XXI and XXIII of article 5, in which it safeguards the property right that will take care of the social function mainly, however its applicability starts to delineate a new legal thought with the new Civil Code of 2002, when the State intervines directly and objective in the private relations, submitting the judiciary a mission to fix in the conflict of private interest what it means the function social.