Legal Question in Intellectual Property in Massachusetts

Formally: the artist's work in Germany would enjoy protection in all of the Berne Convention countries (including the USA) if it satisfies the minimum originality and creativity requirementsl reproduction without a license from the copyright owner would be an infringement. On a practical level, (1) identifying the artist may well be impossible; (2) the artist is highly unlikely to become aware of the infringing T-shirts; (3) you can likely arrive at acceptable licensing terms after the fact if the artist surfaces; and (4) because the works are almost certainly not registered, the artist's remedies in US courts are limited to actual damages and injunctive relief.

Best wishes,

LDWG