If either they decided it was none of their business
Somehow I don't see that happening ...
<In Janeway's ready room. Doorbell chimes.>
Janeway: Enter.
TUVOK: Captain, we've run some fractometric trinary syntax-based algorithms over mr. Paris' tricorder readings and it turns out that the two Ferengi below are not, in fact, the same Ferengi that were present during the Barzan wormhole auction. So it would seem that the Federation cannot be held responsible for their presence and we have no legal basis to interfere, seeing as the Ferengi are not bound by the Prime Directive.
Janeway <voice dangerous>. Mr. Tuvok, that tricorder data was garbled. You never ran that analysis. Do I make myself clear, commander?
Tuvok: I'll yield to your authority, but with all due respect, Captain, why would you...
Janeway: As you may have noticed, I'm really cranky since coffee rations have been lowered and I want to take it out on those pesky Ferengi.