The strange quark can decay via weak charged currents, following the rule that if $|\Delta S|=1$ then $\Delta S=\Delta Q_H$ where $Q_H$ is the hadron charge. The source below states that an $s$-quark can only decay into 'up-type quarks' why is this so? and can a similar thing be said about $\bar s$?
(1) Pal, P.B., 2014. An introductory course of particle physics. Taylor & Francis. (p502, link to Google books)