I don’t think it is. From what I’ve read the unequal treatment of people who live in different states violates the equal protection clause.
I don't see how having different laws for Federal employess and congressmen versus the common people doesn't violate equal protection.
If we're forced to buy social security and forced to buy government healthcare, they should have to buy it as well. Having a tier of laws for the rulers and a tier of laws for the ruled must be unconstitutional.