[MRM]

Your question is far too complex to be answered definitively here. The way the law works is that there is a general rule, then you look for exceptions. You apply the facts of your situation to the general rule, then test it for exceptions, and see what comes out.

In your case the general rule is that the employer can set the terms and conditions of your employment. They could wake up tomorrow and tell you they didn't need you anymore because they had too many employees or you were too expensive and there isn't anything you could do except apply for unemployment. Employers can upgrade the demands and requirements of a position, even while people occupy the job. It may not be fair, but it is generally legal.

The question is whether there is an exception for your situation that takes you out of the general rule for at-will employees. Age discrimination is one, but without a lot more facts, that exception wouldn't apply. A facially neutral excuse to terminate someone, even if it has a discriminatory effect, is generally acceptable. For instance, the company can RIF all high salary employees on the grounds that they're too expensive. Who are the high salary employees? The ones that have been there the longest. And who are they? The oldest. But because the discrimination is based on cost, not age, the cuts are legal. I know, I've done the research. Even if there's a 100% correlation between age and salary, RIFs based on salary are legal.

I'd talk to HR is I were you, in a very nonconfrontational and information-seeking manner, and see if they're going to implement the policy retroactively to you, or whether you're going to be grandfathered in. If they are going to require you to get certified, I don't see how you can avoid it, based on the information you gave here.