should we charge tariff on balls sperms?

When foreigners come into the country, they might have balls, and the balls might have sperms.  There is the risk that the balls will have one or more sperms that make a chick pregnat in the country, costing the country money perhaps.  So if there was a balls tariff, or maybe a refundable balls fee that they could collect nine months after they leave if no one gets born from their balls sperms, then maybe there would be less of such things.