Trademark Licensing and Settlements

Abel owns a trademark for Shpont for his services as an electronic dance music recording artist. Shpont, as an artist, is famous and has consistently released critically acclaimed albums for over two decades. However, Abel has noticed that consumers are paying for less Shpont music every year.

Abel decides to address the situation by exploiting the goodwill of the Shpont mark. Abel announces on Twitter that any apparel company is permitted to use the Shpont mark without any restrictions, provided that 50% of the net revenue is paid to Abel. Dozens of apparel companies leap at the opportunity, and soon the Shpont mark appears on all kinds of t-shirts, sweatshirts, caps, etc. A photographer then starts to use the Shpont mark without permission, and Abel sues for infringement. Does Abel have an enforceable trademark?