US stock futures slipped on Tuesday as markets reopened after the long holiday weekend, starting what is often a seasonally weak month for equities on the back foot. September has historically been the toughest month for stocks, with the S&P 500 averaging a 4.2% decline over the past five years. Sentiment was also weighed by a federal appeals court ruling late Friday that deemed most of President Donald Trump’s global tariffs unlawful. Trump blasted the decision as “highly partisan” and vowed to appeal to the US Supreme Court. At the same time, concerns over the Federal Reserve’s independence linger, with Trump pushing to remove Fed Governor Lisa Cook. This week, Stephen Miran, one of Trump’s nominees, is set to face a Senate Banking Committee hearing. In August, the Dow gained 3.2%, the S&P 500 rose 1.91%, and the Nasdaq Composite advanced 1.58%.