This paper deals with English vowel reduction and focuses on what is generally referred to as the Arab Rule (Ross 1972 i.a.). Vowels tend to reduce if the preceding syllable is light, whereas they do not reduce if the preceding syllable is heavy. Our purpose is twofold: first, based on the scrutiny of Wells (2008), we evaluate the efficiency of the Arab Rule and show that is empirically verified. Second, we propose an analysis of blocking contexts couched within CVCV phonology (Lowenstamm 1996). We use two central notions such as Government and Licensing, and show that vowel reduction only applies to "governing-and-governable" vowels.