In David Griffiths' Introduction to Elemantary Particles book, Problem 1.8 makes me confused. It wants me to write possible decay modes of Ω¯. In the parentheses, there is an explanation.It says "The Ω¯ does in fact decay, but by the much slower weak interaction, which does not converse strangeness". So I think only charge conservation is necessary. Ω¯ ->Σ¯ + π° I think it is possible. Because mass of Ω¯ is greater than mass of Σ¯ + π°. But it is not in possible Ω¯ decays. http://en.wikipedia.org/wiki/Omega_baryon. I am not a native speaker. I apologize you if I make mistake for writing this topic.