Just straight up ban them. Have to pay taxes on investment due to dividends? Well too bad for you.

Just tax them, they'll disappear.

Tax what? The buy back? How does that work? The seller is already paying capital gains tax.

That doesn't require that the government don't tax the profit that allowed the buyback.

The US taxing almost no kind of corporate profit is an oddity, and they can carve more exceptions to any kind of reinvestment they decide.

I recently learned that buybacks and short selling historically have not been legal, its only in recent history that they've been standard practice en large (1982 is when buybacks were legalized, I think)

It’s part of Reaganomics. They weren’t explicitly illegal beforehand though, it just wasn’t clear when they would count as stock price manipulation.