A labor union's local pension fund is teaming up with a peer out of Cincinnati to take on investing titan BlackRock, which they say has structured its iShares family of exchange-traded funds with excessive fees. At the heart of their lawsuit is the amount of money BlackRock executives have taken from the funds' securities lending revenues. But BlackRock says it will defend itself.

The company's securities-lending program has delivered above-average returns to its ETF shareholders over time, BlackRock spokeswoman Caroline Hancock said in an email. "To achieve this, we run the program ourselves while bearing all the costs, rather than outsourcing to third parties as others do," she added.