Well, then a second company could be formed for the purpose of buying shares of the first.
The first company could buy shares in the second. The first company has now bought back its own stock indirectly.
So, there's no point to banning buybacks. If they are economical but somehow banned, they will be emulated.
Buybacks are usually economical as a way to return dollars to stockholders without incurring the immediate taxation that dividends do. Want fewer buybacks? Lower taxes on dividends. Nothing else will reduce them or, as shown above, their emulation in the face of onerous laws.