I checked the SOP and he is not supposed to have the lacing going on in the chest. His chest should be solid black preferably, with a few copper spots allowed. Also, in this picture it looks like his legs are dark slate in color, when they should be light to mid slate with pink showing between the scales (because they have white skin). The bottoms of his feet should be pinkish white, if he has the correct leg and skin color. Additionally, his beak should be horn in color, with some black shading permissible, but instead it appears to be solid black.
Additionally, the standard calls for the shanks to be lightly feathered, and he has no leg feathering at all. That alone is a disqualification, meaning he will get DQ'd out of any show. Sorry
The standard is posted here in this thread:
https://www.backyardchickens.com/threads/marans-sop-discussion-thread.517113/
Edit: This of course all only being applicable in the US, since this thread is for pictures of birds bred to the APA and ABA SOPs. If you're not in the US (you don't have a location listed under your profile so I'm not sure) then this info may or may not apply.