On a server, when someone is deoped or un-whitelisted while whitelist = true and enforce whitelist = true, anyone not on the whitelist is kicked for "Not being on the whitelist" (All OP), but are not stopped from joining again. OP players are supposed to be exempt from whitelist, so either should be allowed on and not kicked or not allowed on at all when enforce whitelist is true (more likely they shouldn't be allowed on at all).

To reproduce

Server Settings:

enforce-whitelist=true
white-list=true

Players as example:

• Test 1
• Test 2
• Test 3

OP list:

• Test 1
• Test 2
• Test 3

Whitelist:

• Test 1
• Test 3

To kick all non-whitelisted players, any of these commands will work:

/whitelist remove Test1
/whitelist remove Test3
/deop Test1
/deop Test2
/deop Test3

If Test1 is un-whitelisted, everyone except Test3 will be kicked. If Test1 is de-oped, Test2 will be kicked.