According to DW, although it is unclear why US President Donald Trump decided to proscribe the outfit, expert consider this move a positive step.
"It is a good sign that the Trump administration is not leaving any impression that it is promoting or tolerating any terrorist group, including those who seek to destabilise Iran," Fatemeh Aman from the Atlantic Council, a US-based international affairs think tank.
It could be seen as a signal to Tehran from Washington that the US was ready to make concessions to the Iranian regime. But Aman is of the view that the designation move could have been more effective if supported by other US actions. "Just targeting anti-Iran groups won't be helpful; the US needs to ensure Iran that it is not seeking regime change in the country," he underlined.
The US also declared the Balochistan Liberation Army (BLA) a terrorist group – a move hailed by Pakistan.
"Jaish al-Adl is clearly a terrorist group, based on its tactics and targets. This is a simple case of the US government giving the group the terrorist designation it deserves. Unlike the case of the BLA, which the US likely designated now because of a desire to ease tensions with Pakistan and China, this can simply be read as a US decision to designate a group that should have gotten the terror label years ago. I don't think there are necessarily any ulterior motives in this case, and we shouldn't necessarily read too much into the timing," Michael Kugelman, a South Asia expert at the Washington-based Woodrow Wilson Center for Scholars, said.
Kugelman opined that the US move against Jaish al-Adl could put more pressure on Islamabad to take action against the group. "The designation may aggravate Iran-Pakistan ties at a moment when Islamabad is trying to maintain a neutral position in the sharpening Saudi-Iranian rivalry," the expert said.
DW also noted that Jaish al-Adl's militant activities have been a bone of contention between Pakistan and Iran for many years. In November last year, Iran's Interior Minister Abdelreza Rahmani-Fazli warned Pakistan that Iranian forces could launch military operations inside Pakistani territory if Islamabad didn't act against the group.
Some reports claim that the banning of Jaish al-Adl probably has more to do with the Afghan peace process than the conflict in the Persian Gulf. And the DW quoted a Pakistani intelligence official, who talked on the condition of anonymity, as saying that Jaish al-Adl could potentially provide recruits to 'Islamic State' (IS) in the Iran-Pakistan border region.
"Since the beginning of the Afghan peace process, there has been an understanding between all stakeholders that IS can pose a common threat to everyone. Thus, the move against Jaish al-Adl is mutually agreed upon," the official added.