The story: Belgium says it has requested the “transfer” back home of an aid worker jailed in Iran. The move comes as a prisoner swap treaty passed by the Belgian government has gone into effect. In parallel, the Iranian president has held a telephone conversation with the Sultan of Oman, a nation with a history of mediating prisoner swaps between Iran and western states.

If a detainee exchange is taking shape, it could see Belgium’s release of a jailed Iranian diplomat—and may pave the way for similar swaps between Iran and Sweden as well as the US.

The coverage: Foreign Minister Hadja Lahbib stated in an Apr. 18 Twitter post that Belgium would on Apr. 19 submit a formal “transfer request” to Iran for...