An employer need not provide company health insurance. Therefore to the extent that it does it is a discretionary benefit. This means that an employer can mandate its terms and conditions. The fact is that not all employees need be treated the same in the workplace. Accordingly unless actionable discrimination is a factor for this difference in employee contributions, your employer's action is perfectly permissable. Additonally, if this is in direct violation of company policy or in some way is prohibted by virtue of a union agreeemnt or employment contract.Note: Actionable discrimination would be because of a person's membership in a legally protected class, for example such as that based on race, religion, gender, etc