No matter if the drug test shows ups negative or positive, if you admit to using marijuana within a three year time period your visa will automatcially get denied. Up until recently this would result in a three year ban, meaning that you couldn't re-apply for a Visa until three years had passed. Think of yourself as lucky, because now it's only a one year ban. He will most definitely get a one year ban and he will be required to submit drug tests when you re-apply. It's a good thing that he was honest and admitted to using marijuana, because if he denied it, and then the test results came back positive, there's a chance he could've gotten a 10 year ban or lifetime ban for fraud.