Only an “interested party” can bring a GAO bid protest. This generally means that a protester must be “an actual or prospective bidder or offeror” with a “direct economic interest” in the contract’s award.
You might ask: is there such a thing as an offeror without a direct economic interest in the outcome of the contract award? It can happen–and a novation may be relevant. In a recent case, GAO held that a pending novation meant that the protester didn’t meet the standard necessary to file a protest.