skyline laws

soo, I was looking on the business section of craigslist the other day and this guy needed a half partner, $25,000 buy in for a pot growing dipensery in CO… Say he goes through with it, grows like a street value of ehh $250k worth of pot… State law its 100% fine, but if the feds want to end this dudes life they can? lol… WTF is the sense of being able to call it legal then!?