It is legal. While in your state, an employer may not discriminate against an employee for being married to a co-worker, this would not constitute actionable discrimination for two reasons:1) It would be discrimination to treat you *worse* than employees not married to co-workers, that's not what's happening here: an employee married to a non-coworker would have to opt for family coverage, too, so you are being treated the same as persons married to non-coworkers.2) Even if you were being treated somewhat differently than fellow employees not married to co-workers, the law does allow some differential treatment: it only requires a "reasonable accommodation" to your protected category or status. By having to have one of you be on the other's plan, you are getting your health coverage: you are not being denied anything of any value. AND it is likely less expensive for the employer to provide a single family plan than two individual plans. It would not be reasonable for the employer to have to pay extra to provide you the same exact thing (the same health coverage) simply because you have a personal preference to be covered separately.