Yes, Major League Soccer (MLS) is a member of FIFA, the international governing body of association football, futsal, and beach soccer. This means that MLS teams and players are subject to FIFA's rules and regulations, and MLS operates within the framework of FIFA's global soccer structure.
In contrast, other high-level sports teams are allowed the convenience and luxury of chartered flights for their games. MLS teams were each permitted four individual privately chartered legs (two matches if the service is roundtrip) for a whole season, but players and coaches grew increasingly upset with such rules.