I remember hearing that this used to be the case, but this is a pretty blatant violation of international law and regulations, and I think by now roaming is also technically disabled in countries that didn't grant them a license.
Their own support site is a bit ambiguous:
> If your new location is not in an authorized territory (marked "Available" or "Waitlist" on the Starlink map), your service may be immediately suspended.
Surely international law can't force StarLink to detect where their terminals are. Or force StarLink to block their signals from leaking into neighbouring countries.
They won't market or distribute their terminals in countries where it is illegal.
So it's up to customs to seize terminals when they cross the borders or communications regulators to seize terminals after they came in.
At this stage, I think StarLink is clamping down on roaming because they don't want to jeopardize their negotiations with the SA government.