But large states cannot do it in a legit manner as they have to follow some constitutional rights of their citizens. Most constitutions of these countries have enough freedom rights paved into them to avoid such blatant action by the government. Besides, the backlash in the media would be unbelievable, the party that does this kind of thing may not find many voters in the next election due to the negative press (at least in technologically advanced nations like USA and Sweden where people are generally aware of online rights).

Which US constitution clause would prohibit the US government from launching a 51% attack?

The fourth amendment?

Where you live sounds very nice.