Wow... 3 weeks? Honestly, I feel bad for him not educating himself on the metabolites of Mary Jane. That shit can stay in your system for 2 months or longer for heavy use (from what I've read anyways.) As a marijuana smoker myself, I both sympathies with him, and shake my head in disappointment at the same time.
To be real, I'm currently trying to get a job myself. I've smoked for a few years, every single day (3-5 drags off a pipe, so not a very heavy user, IMO). I quit smoking about 4 ½ weeks ago, and I'm still not confident I'd pass a drug test. How the hell can a marijuana user expect to pass a drug test in 3 weeks, at least one that clearly uses it every single day, as I would do, with a card & prescription saying I'm legally allowed to?
Plain and simple, Riddle fucked up. He knows the laws and the rules. Regardless of whether the laws and rules are bullshit, they exist for the moment. He clearly didn't learn from them the first time around, and hopefully he's intelligent enough (or someone close to him is) to figure it out now. It's a damn shame, for a fighter to have all his professional fights inside the UFC, and be cut after a win.