Why wasn't chris klein in American wedding?

Klein opted not to return for the last sequel,American Pie: The Wedding, because the script didn't really utilise his character. "Oz and Heather's (Mena Suvari) storyline had ran it's course and I was actually busy doing a play called 'This Is Our Youth' in London. As much as I would've liked to have been a part of it, because those guys are like my family, it didn't work out. It was a case of what can you do?"