Carleton has several policies regarding drugs and alcohol that can be summed in up in just a few words: behave responsibly, don't send yourself to the hospital, and don't set anything on fire. If you follow those rules, you'll never encounter problems. The school sees RAs as crowd control more than anything else. If you're drinking in the hallway, an RA will tell you to take it in your room. They'll never force you to pour it out, even if you're underage-unless you throw up on their door or set up a distillery in the bathroom. The same goes for pot. RAs ignore the smell unless it becomes a problem for the entire floor. The school expects students to police themselves and believe that this trust will breed responsible, adult-like behavior. For the most part, this theory succeeds.
Carleton is a private college, so that means they can bar Northfield police from campus. This means students don't have to worry about police banging on your door if you're underage. Northfield police must get the college's consent to enter residences. Northfield police usually break up off campus parties at 1 a.m., but very rarely do they ticket underage drinkers if they leave the party without causing a ruckus. Campus parties are also broken up at 1 a.m., and campus security will never give you a ticket unless you moon them or set something on fire-and even then, you'll probably get away with just a warning.