I mean, they’re already in rebellion (importing invaders against the wishes of the nation, election fraud, etc)
Not paying tribute to the national is a logical extension of that.
Until now the nation has been very weak in its treatment of rebellion. I guess because they ARE weak, and also because they fear that harsh treatment would blow the issue up.
That has given time for the rebels to imports tens of millions of invaders, and now the problem is too big to avoid.