  A locale, being a complete Heyting algebra, satisfies De Morgan law $(a\vee
b)^*=a^*\wedge b^*$ for pseudocomplements. The dual De Morgan law $(a\wedge
b)^*={a^* \vee b^*}$ (here referred to as the second De Morgan law) is
equivalent to, among other conditions, $(a\vee b)^{**} =a^{**}\vee b^{**}$, and
characterizes the class of extremally disconnected locales. This paper presents
a study of the subclasses of extremally disconnected locales determined by the
infinite versions of the second De Morgan law and its equivalents.
