How was this able to happen?
 

Topps and bowman were supposed to be at "war" with each other. However, in the 1952 Topps set, on a few cards, they used 1951 Bowman photos!

How were they able to do this?

Examples:

1951 Bowman / 1952 Topps Sheldon Jones

1951 Bowman / 1952 Topps Leo Durocher

1951 Bowman / 1952 Topps Les Moss

etc...????

My guess is that both companies licensed the photos from the same source.

Topps and Bowman
 

The Topps And Bowman rivalry involved attempts to get exclusive rights to market player likenesses with candy, gum or confections. Any one could have marketed any player they signed up without those premiums. While Topps later took a lot of their own photos and may have copyrighted them, the "war" with Bowman involved how the likenesses could be packaged and marketed, not the likenesses themselves

In 1982, Topps and Fleer both used the same photo for Rod Carew. Topps' "Rod Carew In Action" was crystal clear. The Fleer regular Carew card, not so much.

That's wild! I was never aware of that and I collected both sets heavily at the time.