You could eventually make UBI a constitutional right. At that point the government controls it in the way they 'control' your right to free speech or to life. In material terms government coercion could deprive you of either, but it would be considered extremely illegitimate for the government to do it. If you want a 'positive right' example, in most countries the government would be considered to be failing its duties if it failed to provide free elementary public education for all citizens, and the logistics of that are more complicated to both provide and verify than a simple cash transfer.

I see it going in much the same way current governments in stable countries don't suddenly show up at your door saying you owe them 95% in tax. Refusing or delaying to pay your UBI would amount to that, an illegal tax.