If, by some chance, Christian Pulisic is to come to MLS, the league has determined the path for how that would happen.
MLS added Pulisic, the USA and Borussia Dortmund's rising star, to its set list of players subject to the league's allocation order, which is reserved for U.S. men's senior and youth national team players and players returning to MLS after being transferred out for more than $500,000. Alejandro Bedoya and Tim Howard made their moves to MLS under that provision this season.
According to MLS's official language: "The players who will be included on the Allocation Ranking List will be determined by Major League Soccer’s player personnel department and club technical staffs and will be updated once each year, during the time window between the end of the MLS regular season and MLS Cup.