You don’t. The only time I’ve ended up on both sides is when I tried to fly German and then realized (probably like Drifter) that the German teamstack was so bad I needed to switch sides to make it more fair.
Also, don’t expect ACG’s board to rule on following any such rule, because the organization on ACGs rules applies only to our server and campaign. Outside of that individuals can do whatever they want, within reason.
Also, “squadron” in ACG means the unit you are assigned to, not the organization as a whole, so that is confusing. I don’t even know many of the people outside my unit.