From Forever 21. Product description:
A muscle tee featuring an Ayd Rand quote graphic which reads "The questions isn't who is going to let me, it's who is going to stop me". Round neckline. Oversized armholes. Raw cut trim. Knit. Lightweight.
Get yours now because unless that quote is licensed, Forever 21 is probably gonna get sued.
Update: Or maybe not, because the quote is a fake. Which kinda makes it even better.
Hat tip (forgive Miss Rand): Tessa Shanks