I'm not a lawyer, and don't pretend to be.
But the race was run on PUBLIC streets, and last time I checked, the public has a right to run on public streets.
Now, if you can PROVE (emphasis on the word prove) that this pair partook of tangible services offered by the race officials that were only to be provided to registrants who paid the race fee -- even something as simple as a drink of public water that happened to be given to them in a paper cup bought for and supplied by the race officials, THEN you might have a case for "theft of services." (Although the judge would probably throw out the case if the only thing that was stolen was a paper cup full of water procured from the city water system.)
But the issue of copying the bib is not the big issue other posters are suggesting, IMHO. Copying the bib only establishes premeditation So they premeditated to do what -- to run on a public street?
Running on a public street is NOT a criminal act. Not even if there is a formal, fee paying race going on at the same time.
This is why I say the issue of copying the bib is a non-issue. It does not, in and of itself, constitute any form of theft - unless, of course, the bandits used the race officials Kinko's copying account to copy the bibs with. Which is highly unlikely.
IF they took something that was provided by the race officials, under the false pretense of having paid race fees, THEN (and only then) do you have a legal case for "theft of services" or any other form of theft, IMHO.
Prove they took refreshment at an aid station, and you've got them.
Prove they took a finisher's medal, or a race shirt, etc and you've got them.
But try to claim "theft of services" because they took advantage of the security that was on the road, or the road closures, or whatever?
That dog just won't hunt.
All they have to do is point out that it was public roadway they were running on, and as a member of the public, they are entitled to run that road any time they want.
Does this situation suck?
You betcha.
I am hoping that somebody might have a photo of them taking aid at an aid station or something, so that the race officials CAN go after them.
But that is the only way they have a chance, legally speaking, IMHO.