Funds duly allocated by the Legislature, which means they must be spent in service of what the Legislature allocated them for. Presidents cannot impound funds since the Impoundment Control Act, so either they need to spend them or convince Congress to change that allocation.
We can argue about the basis for terminating the grants until the cows come home, but this administration through DOGE has made it clear that they're not otherwise going to be spending this money, which is something the president cannot do.
Clawing back and terminating grants without due process is what dictators do; it's the opposite of what supporting and defending the Constitution is.