Can a strong electrolyte be sparingly soluble?
It means that by just adding it to water wont make it dissociate into ions(sparingly soluble) but if current is passed through its solution, it will easily dissociate and give ions. These cases look rare.   

But Curt.F's reasoning looks better :  


  In the low concentration regime where the salt is "soluble", it completely dissociates, but that the solubility limit is just low.