You should duct tape your 2 year olds diaper on if he's taking it off.
If your 2 year old is taking his diaper off and not ready to potty train then using some duct tape on the diaper can help prevent the 2 year old from removing his diaper.
I've duct taped my 2 year olds diaper before and it worked very well and he was not able to get his diaper off.
At first I duct taped only the tabs but eventually he was able to peel the duct tape off and remove the diaper.
After that though I would wrap the duct tape all the way around his waist around the diaper and he was then not able to get the diaper off.
Just don't get the duct tape on his skin but just on the diaper.
I only had to duct tape his diaper for a few months before he gave up on taking the diaper off.
You can use scissors to cut the duct tape off when you change his diaper.