Lying is stating something untrue as true. A dark pattern works on implicit assumptions to get people to believe something without having to state it.

Lying is fraud, plain and simple, the laws and courts nailed that hundreds of years ago. A dark patter may be fraud, or in some way illegal, or may not, depending on details and jurisdiction. Those details might also include intent. An accidentally bad UI that costs customers money is not the same as a UI that purposefully leads customers to the same situation depending on what you're trying to determine (i.e. was the law broken, or is the UI not good).