The topic of relocation in Major League Soccer (MLS) has arisen as the owner of Columbus Crew SC Anthony Precourt has publicly stated his intent to relocate the franchise to Austin, TX. This has never happened in MLS, and the fact that Columbus Crew SC is one of the original MLS franchises only complicates the situation. Officially, we have no concrete answer as to how expansion would formally be handled. But based on previous MLS decisions and other American relocation, we have some idea.
MLS operates as a single entity, with owners of franchises really being investor/operators. Their investment in MLS allows them a seat at the decision making table, as any decision the league makes impacts their investment. Owners still have almost full control over their specific franchise, but one would imagine any move that would dramatically change a franchise's revenue streams would have to be approved by the league as a whole. This could mean a full vote of all owners, or a vote of a sub-committee made up of owners.
While it's unclear at this time exactly how this process will shake out, it's clear we'll have an answer soon as Precourt wishes to make his move before 2019.