Forum:Gravity Bind Vs "can & must"

my friends and I have gotten into an hour long argument over this topic and to settle it once and for all I would like to know who win's.

for example:

Gravity bind is on the field and my friend summon's Ultimate Tyranno and his effect states that he can and must attack all monster on my opponents side of the field and he use's that effect...the question is can he?

Sgtdonut (talk • contribs) 12:31, January 21, 2011 (UTC)Sgtdonut (talk • contribs) 7:31EST, 1/21/2011