Is it illegal in the state of California to have 2 medical insurance coverages?

I just started getting medical benefits from my job. My husband is in the Army and we are now eligible for tricare, but my medical insurance coverage doesn’t end until January of next year. He wants us to enroll ASAP, and it is easier for us to enroll together. My job is saying that it is too late to cancel my coverage. Can I have both? I don’t mind paying for both, I just want to make sure I’m not doing something illegal!