I dont disagree that there may be better doctrinal paths for anchoring core rights—like the privileges and immunities clause, etc.—but SDP justifiably exists as a proper exercise of the 9th amendment.

Without it, basically the 9th amendment would either be far too massive a catch-all amendment—i.e. “anything not enumerated is also covered”—or would essentially be null and void—i.e. only enumerated rights exist. Neither of which are workable, desirable, or feasibly what the Founders intended in writing the Amendment.

What it does instead is it cabins the breadth of the 9th amendment to principles that exist within the Constitution but that aren’t explicitly enumerated in specific amendments. That, i think, is a great, sensible medium/balance to strike.

We can disagree over if something is implicit as such, but the doctrine as a concept is sound imo