50 legislation applied to the instant case was compatible with the requirements of the American Convention. 164. Article 7(2) of the Convention establishes that the deprivation of liberty shall only proceed for the reasons and under the conditions established beforehand by the Political Constitutions of the State Parties or by a law established pursuant thereto. Under the principle of legal codification of the offense, States are obliged to establish, as specifically as possible and “beforehand,” the “reasons” and “conditions” for the deprivation of physical liberty.171 165. Moreover, Article 7(3) of the Convention provides that “no one shall be subject to arbitrary arrest or imprisonment.” The Court has held in previous cases that: No one may be subjected to arrest or imprisonment for reasons and using methods that –although classified as legal– can be considered incompatible with regard for the fundamental rights of the individual, because they are, among other matters, unreasonable, unpredictable, or disproportionate.172 166. In consequence, without prejudice to the lawfulness of the detention, it is necessary to assess, in each case, the compatibility of the legislation with the Convention, understanding that such law and its application must respect the requirements listed below, in order to ensure that this measure is not arbitrary:173 i) that the purpose of the measures that deprive or restrict liberty is compatible with the Convention; ii) that the measures adopted are appropriate to achieve the sought-after purpose; iii) that they are necessary, in the sense that they are absolutely essential to achieve the purpose sought and that, among all possible measures, there is no less burdensome one in relation to the right involved, that would be as suitable to achieve the proposed objective. Hence, the Court has indicated that the right to personal liberty supposes that any limitation of this right must be exceptional;174 and, iv) that the measures are strictly proportionate,175 so that the sacrifice inherent in the restriction of the right to liberty is not exaggerated or excessive compared to the advantages obtained from this restriction and the achievement of the purpose sought. Any restriction of liberty that is not based on a justification that will allow an assessment of whether it is adapted to the conditions set out above will be arbitrary and will thus violate Article 7(3) of the Convention.176 167. That is why, in the instant case, said assessment is related to the compatibility of punitive custodial measures with the American Convention for the control of migratory flows, particularly those concerning irregular migrants, and in this way determine the scope of the State's obligations, within the framework of the State’s responsibility for the violations of the rights enshrined in said treaty. Therefore, the Court shall proceed to evaluate whether the custodial measure applied to Mr. Vélez Loor complied with the requirements mentioned according to which it must be lawful, 171 Cf. Case of Chaparro Álvarez and Lapo Íñiguez, supra note 99, para. 57; Case of Usón Ramírez, supra note 10, para. 145, and Case of Yvon Neptune, supra note 97, para. 96. 172 Case of Gangaram Panday v. Surinam. Merits, Reparations, and Costs. Judgment of January 21, 1994. Series C No. 16, para. 47; Case of Usón Ramírez, supra note 10, para. 146, and Case of Yvon Neptune, supra note 97, para. 97. 173 Cf. Case of Chaparro Álvarez and Lapo Íñiguez, supra note 99, para. 93, and Case of Yvon Neptune, supra note 97, para. 98. 174 Cf. Case of Ricardo Canese v. Paraguay. Merits, Reparations, and Costs. Judgment of August 31, 2004. Series C No. 111, para. 129; Case of Chaparro Álvarez and Lapo Íñiguez, supra note 99, para. 93, and Case of Yvon Neptune, supra note 97, para. 98. 175 Cf. Case of Ricardo Canese, supra note 174, para. 129; Case of Chaparro Álvarez and Lapo Íñiguez, supra note 99, para. 93, and Case of Yvon Neptune, supra note 97, para. 98. 176 Cf. Case of García Asto and Ramírez Rojas, supra note 99, para. 128; Case of Barreto Leiva, supra note 96, para. 116, and Case of Yvon Neptune, supra note 97, para. 98.