The main purpose of this essay is to sustain the thesis of the priority application of international law over domestic law through a methodical and systematic interpretation of the Spanish Constitution of 1978. This qualification is not exclusive of the Spanish case. Constitutional systems such as that applicable in Germany before reunification, both in the Federal and in the Democratic Republic established the equivalence of general international law and domestic laws and, as the case may be, the prevalence of conventional international law. Although pertaining to a different legal system, mention should be made of English common law, so as to point that the Spanish Constitution is not an isolated and unusual case among homogeneous legal spaces, but follows a tradition common to almost all present legal systems.