TSX Group has been blocked from buying 4.85% of alternative trading system Archipelago Holdings LLC.

The TSX planned to purchase the stake in Archipelago from a subsidiary of National Broadcasting Co. However, the deal was subject to the rights of first refusal held by Class A members of Archipelago, which entitled them to purchase the NBC stake.

TSX reports that it has been notified that several of those members have given notice exercising those rights. Consequently, NBC will be required to sell the shares to these current members.

The TSX says that it and Archipelago are continuing to explore opportunities “to serve their common customers more effectively on a North American basis.”