Anonymous wrote:You're funding his college, OP??
This is the sort of thing parents of younger children post. "You're paying for college, by God, you have the last say." OK, lets play that out. OP says to DS "drop GF or no college tuition for you." DS says "OK, I'll just hang out with GF, maybe get a job, whatever." if you follow through, youthful poor judgment becomes a lifelong problem, or at least a problem that will take some time to turn around. Most likely you will cave because you don't want him to sabotage his future, in which case it was an empty threat to being with.
We don;t get to choose our children's partners. Repeat that three times. Ultimately, one day, they will be choosing a partner for life and they'd better have learned for themselves how to make such choices, which means making mistakes along the way. And you ultimately can't control this anyway. OP's DS will be at college and will be able to hang out with and sleep with whomever he wants and he won;t even have to tell you. But you can sure try to infantalize him by controlling this.