It was forbidden to become unclean.
Nonsense -Cofty
"Speak to the Israelites and say to them.." -Lev 18:2 ..... Lev 18:20,24,25 (resulted in uncleanness ) --- It was forbidden to become unclean: not only for the Kohenim but for everyone!
Burying a dead animal, having sex with your wife, results in uncleanness but was not forbidden. Eating a dead animal was forbidden: "..must not.."