Sorry, but the inscription on that ring
is the first line of the Shahada in Arabic. The second line (not shown on the ring), in English, reads "and Muhammad is the Prophet of the God" (the literal meaning of "Allah") or in Arabic "wa Muhammad Rasul-llah". The Shahada is significant in that uttering it out loud and with belief is roughly equivalent to being Baptised in Christianity. Islam is informal that way. Divorce (for a man) involves nothing more than saying three times to the wife, spinning 360 degrees to face her in between each utterance, "I divorce you".
I have seen such rings first hand and could have bought one in any gold sooq (bazaar) in the Middle East. At one such visit I instead opted for an 18 carat crucifix with 14 carat chain. If Obama was a Christian he might have bought and be wearing the same. Maybe he thinks of it as a cool souvenir. You may well disagree, but some of us think his wearing even the coolest souvenir for decades on the wedding ring finger implies a level of commitment worth noticing.