In a strict sense, it may not be, but how a government might fund itself without taxation is a subject for another discussion. It took a constitutional amendmen

In a strict sense, it may not be, but how a government might fund itself without taxation is a subject for another discussion. It took a constitutional amendment to legalize a Federal income tax. Regardless of any moral objections, the income tax is about as legal as it gets[0]. I'm not sure what legal theory would justify mandatory health insurance under the Constitution. [0]I'm aware of various claims that the income tax really isn't legal, but I don't think any of them attack its constitutional authority.