Didn't think so.
It clearly says that all states must respect the slavery laws of slave states. That is pretty much declaring slavery legal.
Also the fact that it banned congress from stopping the importation of slaves until 1808 is another clue that it considered the practice of slavery legal.
If it banned congress from halting the slave trade until 1808, doesn't that imply the slave trade was regarded as legal prior to 1808? And if the slave trade was legal, does that not also imply that slavery itself was legal?