Technically... you can in all but one circumstance: modern US constitutional law.
I don't think any country has the same laisezz-faire approach to buying politicians... certainly not in the name of free speech. I don't think the argument has even been made.
That said, even in the US there isn't a real constitutional barrier to doing something about money in politics. You could make candidates wear sponsorships on their jerseys, like racecar drivers. No free impediment. That's a joke example, but you see my point. That particular ruling is not an actual barrier, the barrier is a legislative majority.
The US is what I was talking about re: "money === speech," e.g. Citizens United.
I'll less interested in sound byte-like fixes like "wear sponsorships on their jerseys" and more with what you can realistically change without overturning Supreme Court precedent or ignoring the Constitution entirely.
I think the joke/soundbite example demonstrates a point: The Jersey Rule would be ok constitutionally. Even with that ruling standing, there is plenty of room for legislators to fix "money in politics" practically, without contradicting the SC. Laurence Lessig has some of the best known proposals.
The problem, as I see it, is status quo bias within any congress/parliament. Actually removing money from politics crashes their industry, puts all their friends out of work, and challenges their power. Every unsuccessful candidate, campaign manager, staffer, and such makes their living this way. Every successful candidate was successful at this way of doing politics.
It's a similar problem to legislation (or even customs) that would enable 3rd parties to succeed. It's against the interests of the Republican and Democratic parties, so it won't happen.
Citizens United was not about buying politicians: it was about a group of citizens wishing to show a movie critical of a politician. How is that not legitimately-protected speech?
I don't think any country has the same laisezz-faire approach to buying politicians... certainly not in the name of free speech. I don't think the argument has even been made.
That said, even in the US there isn't a real constitutional barrier to doing something about money in politics. You could make candidates wear sponsorships on their jerseys, like racecar drivers. No free impediment. That's a joke example, but you see my point. That particular ruling is not an actual barrier, the barrier is a legislative majority.