After several games I finally found a place to test this. After 40 seconds I got shot. Tried again, got shot after 30 seconds. Oh, man, these maps made for camping! My normal play style isn't rushing but I never saw any indication of the kick mechanism so I had to try to do it.
I did figure it out. First, the warning is in the killfeed, so it may as well be invisible unless you're actively looking for it. It takes around a minute to kick you, sometimes a few seconds more, sometimes a few seconds less. You can move your look/aim around all you want & even enter and leave ADS multiple times and it will still kick you. Shooting my gun didn't make it go away, just reset it. The only thing I didn't get the chance to test was whether the kill with my tripmine would reset the clock. I got shot 5 seconds before the kick-time-window.
1) The problem was in the Gun Game but somehow the solution is applied to everything. You can't solve a problem in one mode without changing all of them?
2) 1 minute is stupid. I should be able to take care of (insert random quick thing in life) and come back in more than a minute and continue playing. We don't all live and breathe CoD while consuming only Doritos and Dew. Some of us need 90 seconds to make a sandwich or cook a Totinos pizza, damn it!
3) Even when you apply consistent, different, non-patterned inputs to the controller, meaning in should be obvious you're there, you still get kicked. Unless of course that input comes from the left stick. No loopholes there, nope.
4) People are getting kicked while they operate scorestreaks. I repeat: people who are so involved in the game that they got enough in scorestreaks to require more than 1 full minute of time to deploy and operate are being kicked because they stopped moving to bring those scorestreaks in. That's like the baseball manager accusing the player that just hit a homerun of lollygagging for not sprinting around the bases.
The biggest point: everyone who's thinking right now "Ha! Stupid campers", remember this. If you're ok with Acti dictating that a playstyle you don't use will be penalized by removal from the game then you're ok with them penalizing any playstyle by any method up to and including removal from the game. Don't cry when it happens to you and don't expect any sympathy.