In McDonald, here is how Justice Stevens describes liberty protected by the “liberty clause” of the Constitution:

Implicit in Justice Cardozo’’s test is a recognition that the postulates of liberty have a universal character. Liberty claims that are inseparable from the customs that prevail in a certain region, the idiosyncratic expectations of a certain group, or the personal preferences of their champions, may be valid claims in some sense; but they are not of constitutional stature. Whether conceptualized as a ““rational continuum”” of legal precepts, Poe, 367 U. S., at 543 (Harlan, J., dissenting), or a seamless web of moral commitments, the rights embraced by the liberty clause transcend the local and the particular.

I still think Kennedy did a better job in Lawrence v. Texas:

The instant case involves liberty of the person both in its spatial and more transcendent dimensions.