The Egyptian military’s recent flooding of tunnels at the border between Egypt and Gaza is its most aggressive attempt yet to restrict smuggling since Israel imposed a blockade on the Palestinian territory in 2005. Sewage water is reportedly being used to weaken the tunnels’ structure, sometimes trapping smugglers inside.

Although such efforts are not new, their endorsement by the Muslim Brotherhood is.

The Hamas government in Gaza, which regulates the tunnels and collects a tax on activity through them, has condemned the flooding. It says the trade — which is mostly in consumer goods and fuel, not weaponry — is necessary to counter the impact of Israel’s embargo, and it is calling on the Egyptian government to open the Rafah border crossing to allow for unfettered supplies. When the Muslim Brotherhood was in the opposition, it backed this position. But it has not changed Egypt’s policy since Mohamed Morsi was elected president, even after the mini war between Hamas and Israel last November.

The Egyptian government’s rationale is that the tunnel trade goes two ways. Not only are weapons coming in to resupply Hamas’s fighters — the reason Israel and the West want the tunnels closed — but weapons and trained fighters from Gaza are entering Egypt and joining the ranks of Islamist militants in the Sinai Peninsula. These militants are believed to be behind the deadly August 2012 attack on Egyptian soldiers near the border.

Cairo’s official line is that, since Israel is an occupying power in Gaza, under international law it is responsible for the territory and should open its borders. The more important reason, though, is that it fears Israel wants nothing more than to dump its Gaza problem on Egypt’s lap. Indeed, even as Israel backs the blockade — with, in essence, the assent of the West — some of its officials are increasingly calling on Egypt to open Rafah, and so take responsibility for the Gazan economy.

Egyptian officials say they have already opened Rafah to allow for the crossing for humanitarian goods, which is as much as can be expected of them under international law. But clearly they are cautious about the consequences of a wider opening. For Egypt, the risk is not only further entrenching the divide between Gaza and the West Bank it has tried to heal through inter-Palestinian reconciliation talks, but also creating new security and political problems. The greatest of those, no doubt, would be making itself responsible for Hamas’s behavior toward Israel.

Meanwhile, however, pressure is mounting. Gazans are getting used to goods from Egypt, which are cheaper than those from Israel, and a smuggling route, once established, is hard to dismantle. The illicit trade has also criminalized the economy of eastern Sinai, turning the Bedouin tribes that control most of the tunnels into powerful mafias that defy state authority.

There may be no easy solution for Israelis or Egyptians; neither group wants responsibility for Gaza. Ideally, of course, Gazans would need no one’s help: They should be free to import from and export to the outside world, or at least their fellow Palestinians in the West Bank.

Opening Gaza’s border with Egypt could be part of that solution, but Israel would also have to allow trade between the Palestinian territories that are now separated. Then, the tunnels that fulfill much of Gaza’s basic humanitarian and consumer needs would no longer be necessary. And Egypt could focus on stemming weapons smuggling, as the international community demands of it, while securing its eastern border.

The status quo was difficult under Hosni Mubarak. It’s not likely to be sustainable under Mohamed Morsi.