If multiple device remotes are controlling it, then it is either using the exact same codes as whatever other device you have (which shouldn't happen if it was designed properly), or it has a poor quality IR reception system incapable of rejecting commands that aren't specifically intended for it (ie. it sees any sort of pulse that "looks about right" and responds).

There really isn't a whole lot you can do about this - the fault lies with the lighting system.

If you must have remote control over it, the only workable solution is to get an RF universal remote with an RF basestation with addressable IR outputs, and then you can run an emitter from the basestation to the lighting system's IR receiver and ensure that it only ever receives its own signals. The problem with this is RF remotes with addressable outputs start at around $400-500.