You mean as in an auctioning platform? That's legally a bit harder to achieve, as auctions usually have the rule that if nobody outbids you, then your offer is binding. To enforce that, instances would need to verify your identity. That's easy for a larger company to do, but not that easy for hobbyists.

And then, to be federated, you would also need to make sure that other instances that you federate with uphold that standard.

Also, if you do auctions across international borders, how do you even prosecute somebody who does not obey the rules of an auction?