Map makers are currently not able to disallow player movement completely. Players are still able to move by sprint jumping (Default Keys: Ctrl+W+Space) even when the effects 'Slowness' and 'Jump Boost' 128 are active (Jump Boost 128 negates jump). Instead of using Jump Boost you can also set generic.movementSpeed to 0 using attribute modifiers
Slowness (using /effect):
/effect @p 2 100 10 true
Slowness (using attribute modifiers):
/replaceitem entity @p slot.armor.feet leather_boots 1 0 {AttributeModifiers:[{Operation:0,UUIDLeast:1,UUIDMost:1,Amount:-0.1,AttributeName:generic.movementSpeed,Name:Freeze}]}
Jump Boost:
/effect @p 8 100 128 true
Disallowing the player to sprint if the player is not able to move at all would allow map makers to freeze players completely.
Related issues
Comments

Dupe of MC-2112
Besides that, effects beyond level IV are not supported: MC-10755