[Colonel Kangaroo]

The US Constitution did not contain anything like this:

"No bill of attainder, ex post facto law, or law denying or impairing the right of property in negro slaves shall be passed."

[DoodleDawg]

Not to mention a clause protecting slave imports.

[jeffersondem]

“The US Constitution did not contain anything like this:
“No bill of attainder, ex post facto law, or law denying or impairing the right of property in negro slaves shall be passed.”

Are you absolutely certain about these points?

I was thinking the United States constitution does prohibit a Bill of Attainder and ex post facto Law.

Maybe somewhere around Section 9, Article I. Check it out.