Your local muzzleloader club must have a Federal License to sell black powder if they are buying it by the case and selling it directly to its members.
That is the only way they can legally do that.
There is another way they can order large amounts of powder for the members but, the individual members must first pay for the powder before the order is placed.
Then, the member who is collecting the money can serve as an agent for the group and order the powder.
When it arrives, the agent then distributes the shipment to the members who have already paid for their share.
Under no circumstances (except in cases where the club has a Federal License) can the agent or the club he's a part of, sell any of the powder to anyone who was not part of the initial order.
That is the only way they can legally do that.
There is another way they can order large amounts of powder for the members but, the individual members must first pay for the powder before the order is placed.
Then, the member who is collecting the money can serve as an agent for the group and order the powder.
When it arrives, the agent then distributes the shipment to the members who have already paid for their share.
Under no circumstances (except in cases where the club has a Federal License) can the agent or the club he's a part of, sell any of the powder to anyone who was not part of the initial order.