This is something of an old chestnut, but I still see it routinely, particularly in the letter and order that bear its name. The cease-and-desist letter is a staple of IP law. You see it a lot in settlement agreements too.
For the record, cease and desist mean the same thing. So a cease-and-desist letter makes about as much sense as a repayment-and-requital plan, a hiring-and-engagement agreement, or an order staying and abating a case. Just pick one. Better yet, just say “stop”.
I’ve heard a few stories of how this particular folly arose, including one regarding the derivation of the two terms. I think the explanation lies in the perceived (but inaccurate) difference in the nuance between the two words. I think most people read “cease” as the act of stopping and “desist” as the act of not starting (perhaps as a cousin or case of mistaken identity with “resist”). So, naturally, some lawyer was trying to prevent an uncharitable interpretation that would allow someone to stop doing something and then start back up again right away. Hence, not merely ceasing but also desisting. And, as with most legal language issues, the practice spread.
Please stop. Or cease. Or desist.