(Photo by Gary Hershorn/Getty Images) · Gary Hershorn via Getty ImagesAritzia (ATZ.TO) is expected to post strong second quarter earnings, but analysts warn new U.S. tariff rules could pressure margins and temper its growth outlook. The change, effective Aug. 29, affects Aritzia's practice of fulfilling a portion of U.S. online orders from Canada. Stephen MacLeod, an analyst at BMO Capital Markets, says the tariff backdrop remains fluid, representing a 50 to 75 basis point headwind. He argues that Aritzia’s growing U.S. footprint and brand appeal leave it well-positioned to weather the challenge. Still, retail analyst Bruce Winder cautions that the U.S. consumer environment is tough right now, with job losses piling up.