States have always hidden, tortured, and killed their citizens. Good states do it very, very rarely, in secret, and as an extraordinary exception to normal rule. Bad states do it whenever they like and in response to any discomfort at all. I think it was Saddam (or Stalin?) that said something like "You have a man. You have a problem. No more man. No more problem."
When the U.S. started droning its own citizens a decade ago, we libertarians said that this was a very bad, no good, horrible idea. You can't treat your own citizens this way.
Looking back, that statement was too idealistic. What happened next was a discussion about ticking bombs, people planning to use WMD, and so on. Nothing much happened. The droning continued.
Next the Russians decided to use nerve gas in London (!) to kill somebody they didn't like. This past week, the Saudis decided to lure somebody into their Turkish embassy where it looks like he was tortured, killed, and chopped up into little pieces. Now we have the president of Interpol vanishing. One hopes the Chinese are at least polite enough about it not to be so braggadocious.
What we're learning from this sorry series of events is that if a leading nation does it systematically and publicly, the rest will too. There are no special "The U.S. gets to do it but nobody else can" cards to hand out.
It is quite disturbing. I expect the trend to continue.