Is there any way to remotely disable a command block?

Try setting the command block to chain and conditional and chaining it after a repeating command block that checks if a lever is flicked, the command should look something like this: /execute if block <coordinates to the lever> minecraft:lever[powered=true]

I assume you want to disable a repeating command block, by toggling it from "always active" to "needs redstone". That can be done by setting its "auto" NBT tag to false, for example like this:

/data merge block 12 34 56 {auto:0}