The volatile cannabis sector is on the upswing in September, boosting a group of exchange-traded funds that have largely struggled over the past two years as legalization of marijuana in the U.S. remains in limbo. The AdvisorShares Pure US Cannabis ETF (MSOS) has jumped 18% in the first four trading days of the month, building on a rally that began in late August. That makes it the best-performing fund so far this month, of funds with at least $200 million in assets, according to FactSet. Smaller funds such as the Roundhill Cannabis ETF (WEED) and the ETFMG U.S. Alternative Harvest ETF (MJUS) have also surged. MSOS 1M mountain Weed stocks are surging in September, as shown by the MSOS ETF. The portfolio for the MSOS ETF consists largely of swaps on stocks that trade over the counter in the U.S., such as Green Thumb Industries. That company announced a $50 million stock buyback program earlier this week. The volatile sector may be getting a boost from lawmakers in Washington. Politico reported earlier this week that the Senate was making progress on a cannabis banking deal. Still, the hot week makes only a small dent in the long-term losses for the funds. The MSOS is down more than 30% since its inception in 2020, and more than 80% since its record high in February 2021. The struggles for marijuana ETFs have extended beyond price movements, as cannabis remains illegal at the federal level. AdvisorShares closed a different cannabis fund in its lineup last month . The MJUS ETF is being sold to Amplify ETFs following legal issues with ETFMG.