No he cannot. There are Colorado laws that say like if a Dr making tons of money cannot go be a doorman somewhere for less pay if he has obligations just because. That is called earning potential! It is sad men don't see that child support is to support the children they brought into the world. If he loses his job they will garnish his unemployment. His girlfriend doesn't factor in however it will be taken into consideration that his bills are half of what they are as he has a "roomate" to help him with those bills!
Go find your local city offices, go in and talk to them. If he is purposely not working to avoid paying out what was agreed they can bring him back into court.
He cannot just not pay.
I was worried as my ex makes good money and wants to move closer to his girlfriend in another town (he lives out of state), there are laws preventing him from just quitting his job because he wants to move though. He has a legal obligation to make his earning potential and support his children. I just researched all of this.
My ex says I take advantage too, it is ridiculous and men sometimes are so blind with resentment they do not realize that they are just as responsible for giving their children the best life possible, which means working hard and paying support! I just ignore what he says, he has told anyone that listens poor him having to pay out so much money a month, but guess what? I am here raising our kids 24/7, so tough if he is bitter and full of resentment, he still will be responsible and help me financially raise our children. He left me and moved out of state. So he doesn't even contribute to taking them every other weekend.
You can seek mediation too, a lot less money but they will bring it all to the table, what it costs you to raise the kids, vs what he has to pay out personally and what his bills are, then take into consideration your earning potential and his.
Just fight! Kids get caught in the crossfire of bitterness in divorce and that breaks my heart.