Whatever age group they pick, or whatever age limitation they put will be unfair to someone because they won't have the guts to include all those who were brought here as children.

"you were brought here as a 13 year old? That's almost an adult..no soup for you!"
"you were brought here as a 4 year old but are now 32? You're an adult now, no soup for you!"
"you're a 22 year old Russian bride who is marrying an 80 year old white guy who met you on his sex tourism trip? Welcome to America!"