Prop 187 was passed in 1994. While Cruz was in Harvard and Bush just became governor elect. How or why would Cruz advise Bush on this in 1999?
Cruz was Bush’s domestic policy adviser in 1999.
Proposition 187 was still talked about a lot, and Bush wanted to have a policy statement on it.
http://www.nytimes.com/interactive/2015/12/18/us/politics/immigration-document.html