In the US, wouldn't that require a constitutional amendment? I thought Citizens United declared money to be free speech (paraphrasing) .
A constitutional amendment would nuke the current limitations, but it's impossible in practice for us to get there. On the other hand, as we've seen as of late, no decision by the Supreme Court is set in stone, so we could, in theory, get Citizens rolled back and then some. That also seems unlikely in the short term.
Not that this is in any way likely to happen, of course.
Notably, the Constitution does not grant the court the power of judicial review. The court granted itself that right. So in a battle between precedent and the text of the Constitution, I hope the latter would win.