Can an employer terminate a non-discretionary bonus program and not pay us our bonuses earned?

Our non-discretionary bonus program was quantified by the revenue generated by the projects we worked on and the overall profitability of those projects. e.g. If I worked on a project that was sold at a 25% gross margin and that job was completed at a 25% gross margin or better, I would be entitled to .3% of the sale price of that project. So if that project was sold for $100,000 I would received $300 towards my bonus. This program was in place for 2 years and we worked really hard to secure large projects, often working nights and weekends to accomplish those objectives, only to have the rug pulled out from under us days prior to our next quarterly bonus payout. Many of us, myself included, relied on those bonus payouts to our detriment in the form of making non-refundable deposits, purchasing additional PTO offered by our employer etc.