What is the military industrial complex?

It is many things, hard to pin down to just one thing. Yes it is consitutional, the byproduct of capitalism run amok. President Eisenhower was ahead of his time in sounding the alarm on that.

Though it may not be a straight-up Nazi-gestapo radical regime, the complex can easily be perceived as such. Thank God for having a 1st Amendment to allow us to speak-out against tyrannical tendencies as inadvertent as they may be. It's the military industrial system as a whole that becomes so massive, cumbersome, and out of control that makes it seem as a dominating force over American values.

And for once I applaud our current commander-in-chief for curbing down the complex, whether politically motivated or not.

http://www.nbcnews.com/news/us-news/u-s-cracking-down-militarization-local-police-n360381

That is a difficult question. If you go by the basis of a limited government, then I think some could find an easier way to justify it as it is the private market influencing the military.

However, as we are seeing most days now, this private influence is pushing the military to consider things it does not necessarily need - a new tank that the Army does not want, a replacement for the A-10 that isn't even a CAS platform, etc.

Eisenhower warned of the MI Complex in his farewell speech. It has corrupted the thought of the Pentagon & pushes for its own favor, many times selling to both ends of the conflict.

Until it is found to be treasonous or otherwise detrimental to the country, I do not know that you could definitively prove it is unConsitutional.